feat(logging): gcp error reporting (#11355)

# Which Problems Are Solved

Zitadel Errors (`zerrors` package) are logged by default. This change
add more verbose error reporting through log output, including
compatibility with GCP error reporting if enabled.

# How the Problems Are Solved

Errors can now carry their "report location" and a stack trace. "Report
location" is enabled by default, while stack-traces are disabled. Our
new [`zitadel/sloggcp`](https://github.com/zitadel/sloggcp) package
provides the GCP error reporting handler for `slog`.

The following section displays the different formats for the same error
(User not found). Newlines and formatting of output is applied for
readability and is not part of the actual log output.

<details>

<summary>Default text output</summary>

```
time=2026-01-15T14:27:20.625+01:00
level=WARN
source=/home/tim/Repositories/zitadel/zitadel/internal/api/grpc/gerrors/zitadel_errors.go:57
msg="User could not be found (COMMAND-bd4ir1mblj)"
domain.instance_host=localhost:8080
domain.protocol=http
protocol=connect
service=zitadel.user.v2.UserService
http_method=POST
path=/zitadel.user.v2.UserService/DeleteUser
request_id=d5keme0ednc50mm74bfg
duration=66.761569ms
TraceID=319374baa56acc2dbd1d0179f1bbec9f
SpanID=541621b0abea7ff1
err.kind=NotFound
err.message="User could not be found"
err.id=COMMAND-bd4ir1mblj
err.reportLocation.filePath=/home/tim/Repositories/zitadel/zitadel/internal/command/user_v2.go
err.reportLocation.lineNumber=140
err.reportLocation.functionName=github.com/zitadel/zitadel/internal/command.(*Commands).RemoveUserV2
```

</details>

<details>

<summary>Default JSON output</summary>

```json
{
  "time": "2026-01-15T14:30:59.280497754+01:00",
  "level": "WARN",
  "source": {
    "function": "github.com/zitadel/zitadel/internal/api/grpc/gerrors.ZITADELToConnectError",
    "file": "/home/tim/Repositories/zitadel/zitadel/internal/api/grpc/gerrors/zitadel_errors.go",
    "line": 57
  },
  "msg": "User could not be found (COMMAND-bd4ir1mblj)",
  "domain": { "instance_host": "localhost:8080", "protocol": "http" },
  "protocol": "connect",
  "service": "zitadel.user.v2.UserService",
  "http_method": "POST",
  "path": "/zitadel.user.v2.UserService/DeleteUser",
  "request_id": "d5keo4oednc6klmo3vbg",
  "duration": 54229055,
  "TraceID": "daa21183bd8da5da56969b0ea45f4388",
  "SpanID": "70da728e3086c104",
  "err": {
    "kind": "NotFound",
    "message": "User could not be found",
    "id": "COMMAND-bd4ir1mblj",
    "reportLocation": {
      "filePath": "/home/tim/Repositories/zitadel/zitadel/internal/command/user_v2.go",
      "lineNumber": 140,
      "functionName": "github.com/zitadel/zitadel/internal/command.(*Commands).RemoveUserV2"
    }
  }
}
```

</details>

When stack trace is enabled, using a standard logger,
it is logged under the `stackTrace` key.

<details>

<summary>Standard JSON format with stack trace</summary>

```json
{
  "time": "2026-01-15T14:36:56.522692368+01:00",
  "level": "WARN",
  "source": {
    "function": "github.com/zitadel/zitadel/internal/api/grpc/gerrors.ZITADELToConnectError",
    "file": "/home/tim/Repositories/zitadel/zitadel/internal/api/grpc/gerrors/zitadel_errors.go",
    "line": 57
  },
  "msg": "User could not be found (COMMAND-bd4ir1mblj)",
  "domain": { "instance_host": "localhost:8080", "protocol": "http" },
  "protocol": "connect",
  "service": "zitadel.user.v2.UserService",
  "http_method": "POST",
  "path": "/zitadel.user.v2.UserService/DeleteUser",
  "request_id": "d5kequ0ednc7lphvgfn0",
  "duration": 57820793,
  "TraceID": "1b05d2b01306f2a64feb1a24b65a89c5",
  "SpanID": "c5ff35a27a917764",
  "err": {
    "kind": "NotFound",
    "message": "User could not be found",
    "id": "COMMAND-bd4ir1mblj",
    "reportLocation": {
      "filePath": "/home/tim/Repositories/zitadel/zitadel/internal/command/user_v2.go",
      "lineNumber": 140,
      "functionName": "github.com/zitadel/zitadel/internal/command.(*Commands).RemoveUserV2"
    },
    "stackTrace": "goroutine 673 [running]:\nruntime/debug.Stack()\n\t/usr/lib/go/src/runtime/debug/stack.go:26 +0x8e\ngithub.com/zitadel/zitadel/internal/zerrors.newZitadelError(0x5, {0x0, 0x0}, {0x6af7719, 0x12}, {0x6aff994, 0x14})\n\t/home/tim/Repositories/zitadel/zitadel/internal/zerrors/zerror.go:139 +0x1df\ngithub.com/zitadel/zitadel/internal/zerrors.ThrowNotFound({0x0, 0x0}, {0x6af7719, 0x12}, {0x6aff994, 0x14})\n\t/home/tim/Repositories/zitadel/zitadel/internal/zerrors/not_found.go:6 +0x70\ngithub.com/zitadel/zitadel/internal/command.(*Commands).RemoveUserV2(0xc0035a4008, {0xa3c1410, 0xc003ded5c0}, {0xc0029693a0, 0x3}, {0x0, 0x0}, {0xd550a60, 0x0, 0x0}, ...)\n\t/home/tim/Repositories/zitadel/zitadel/internal/command/user_v2.go:140 +0x711\ngithub.com/zitadel/zitadel/internal/api/grpc/user/v2.(*Server).DeleteUser(0xc00272d080, {0xa3c1410, 0xc003ded5c0}, 0xc002ebf180)\n\t/home/tim/Repositories/zitadel/zitadel/internal/api/grpc/user/v2/user.go:191 +0x3f1\nconnectrpc.com/connect.NewUnaryHandler[...].func1({0xa405e70, 0xc002ebf180})\n\t/home/tim/go/pkg/mod/connectrpc.com/[email protected].1/handler.go:51 +0x17e\nconnectrpc.com/connect.unaryThunk.func1({0xa3c1410, 0xc003ded5c0}, {0xa405e70, 0xc002ebf180})\n\t/home/tim/go/pkg/mod/connectrpc.com/[email protected].1/interceptor.go:120 +0xd9\ngithub.com/zitadel/zitadel/internal/api/grpc/server/connect_middleware.ActivityInterceptor.func1.1({0xa3c1410, 0xc003ded5c0}, {0xa405e70, 0xc002ebf180})\n\t/home/tim/Repositories/zitadel/zitadel/internal/api/grpc/server/connect_middleware/activity_interceptor.go:20 +0x1b1\nconnectrpc.com/connect.unaryThunk.func1({0xa3c1410, 0xc003ded4d0}, {0xa405e70, 0xc002ebf180})\n\t/home/tim/go/pkg/mod/connectrpc.com/[email protected].1/interceptor.go:120 +0xd9\ngithub.com/zitadel/zitadel/internal/api/grpc/server/connect_middleware.ServiceHandler.func1.1({0xa3c1410, 0xc003ded4d0}, {0xa405e70, 0xc002ebf180})\n\t/home/tim/Repositories/zitadel/zitadel/internal/api/grpc/server/connect_middleware/service_interceptor.go:22 +0x283\nconnectrpc.com/connect.unaryThunk.func1({0xa3c1410, 0xc003ded4d0}, {0xa405e70, 0xc002ebf180})\n\t/home/tim/go/pkg/mod/connectrpc.com/[email protected].1/interceptor.go:120 +0xd9\ngithub.com/zitadel/zitadel/internal/api/grpc/server/connect_middleware.validate({0xa3c1410, 0xc003ded4d0}, {0xa405e70, 0xc002ebf180}, 0xc0031bff60)\n\t/home/tim/Repositories/zitadel/zitadel/internal/api/grpc/server/connect_middleware/validation_interceptor.go:35 +0x1bd\ngithub.com/zitadel/zitadel/internal/api/grpc/server/connect_middleware.ValidationHandler.func1.1({0xa3c1410, 0xc003ded4d0}, {0xa405e70, 0xc002ebf180})\n\t/home/tim/Repositories/zitadel/zitadel/internal/api/grpc/server/connect_middleware/validation_interceptor.go:15 +0x85\nconnectrpc.com/connect.unaryThunk.func1({0xa3c1410, 0xc003ded4d0}, {0xa405e70, 0xc002ebf180})\n\t/home/tim/go/pkg/mod/connectrpc.com/[email protected].1/interceptor.go:120 +0xd9\ngithub.com/zitadel/zitadel/internal/api/grpc/server/connect_middleware.ExecutionHandler.func1.1({0xa3c1410, 0xc003ded4d0}, {0xa405e70, 0xc002ebf180})\n\t/home/tim/Repositories/zitadel/zitadel/internal/api/grpc/server/connect_middleware/execution_interceptor.go:39 +0x376\nconnectrpc.com/connect.unaryThunk.func1({0xa3c1410, 0xc003ded4d0}, {0xa405e70, 0xc002ebf180})\n\t/home/tim/go/pkg/mod/connectrpc.com/[email protected].1/interceptor.go:120 +0xd9\ngithub.com/zitadel/zitadel/internal/api/grpc/server/connect_middleware.QuotaExhaustedInterceptor.func1.1({0xa3c1410, 0xc003ded4d0}, {0xa405e70, 0xc002ebf180})\n\t/home/tim/Repositories/zitadel/zitadel/internal/api/grpc/server/connect_middleware/quota_interceptor.go:25 +0x42d\nconnectrpc.com/connect.unaryThunk.func1({0xa3c1410, 0xc003ded4d0}, {0xa405e70, 0xc002ebf180})\n\t/home/tim/go/pkg/mod/connectrpc.com/[email protected].1/interceptor.go:120 +0xd9\ngithub.com/zitadel/zitadel/internal/api/grpc/server/connect_middleware.TranslationHandler.func1.1({0xa3c1410, 0xc003ded4d0}, {0xa405e70, 0xc002ebf180})\n\t/home/tim/Repositories/zitadel/zitadel/internal/api/grpc/server/connect_middleware/translation_interceptor.go:18 +0x94\nconnectrpc.com/connect.unaryThunk.func1({0xa3c1410, 0xc003ded4d0}, {0xa405e70, 0xc002ebf180})\n\t/home/tim/go/pkg/mod/connectrpc.com/[email protected].1/interceptor.go:120 +0xd9\ngithub.com/zitadel/zitadel/internal/api/grpc/server/connect_middleware.authorize({0xa3c1410, 0xc003dec000}, {0xa405e70, 0xc002ebf180}, 0xc00321c040, {0xa3f0a70, 0xc0004ebc70}, {{0xc000d2fc80, 0x9, 0x9}}, ...)\n\t/home/tim/Repositories/zitadel/zitadel/internal/api/grpc/server/connect_middleware/auth_interceptor.go:42 +0x894\ngithub.com/zitadel/zitadel/internal/api/grpc/server/connect_middleware.AuthorizationInterceptor.func1.1({0xa3c1410, 0xc003dec000}, {0xa405e70, 0xc002ebf180})\n\t/home/tim/Repositories/zitadel/zitadel/internal/api/grpc/server/connect_middleware/auth_interceptor.go:17 +0x151\nconnectrpc.com/connect.unaryThunk.func1({0xa3c1410, 0xc003dec000}, {0xa405e70, 0xc002ebf180})\n\t/home/tim/go/pkg/mod/connectrpc.com/[email protected].1/interceptor.go:120 +0xd9\ngithub.com/zitadel/zitadel/internal/api/grpc/server/connect_middleware.LimitsInterceptor.func1.1({0xa3c1410, 0xc003dec000}, {0xa405e70, 0xc002ebf180})\n\t/home/tim/Repositories/zitadel/zitadel/internal/api/grpc/server/connect_middleware/limits_interceptor.go:31 +0x3b7\nconnectrpc.com/connect.unaryThunk.func1({0xa3c1410, 0xc003dec000}, {0xa405e70, 0xc002ebf180})\n\t/home/tim/go/pkg/mod/connectrpc.com/[email protected].1/interceptor.go:120 +0xd9\ngithub.com/zitadel/zitadel/internal/api/grpc/server/connect_middleware.toConnectError({0xa3c1410, 0xc003dec000}, {0xa405e70, 0xc002ebf180}, 0xc00321c060)\n\t/home/tim/Repositories/zitadel/zitadel/internal/api/grpc/server/connect_middleware/error_interceptor.go:21 +0x8a\ngithub.com/zitadel/zitadel/internal/api/grpc/server/connect_middleware.ErrorHandler.func1.1({0xa3c1410, 0xc003dec000}, {0xa405e70, 0xc002ebf180})\n\t/home/tim/Repositories/zitadel/zitadel/internal/api/grpc/server/connect_middleware/error_interceptor.go:15 +0x85\nconnectrpc.com/connect.unaryThunk.func1({0xa3c1410, 0xc003dec000}, {0xa405e70, 0xc002ebf180})\n\t/home/tim/go/pkg/mod/connectrpc.com/[email protected].1/interceptor.go:120 +0xd9\ngithub.com/zitadel/zitadel/internal/api/grpc/server/connect_middleware.AccessStorageInterceptor.func1.1({0xa3c1410, 0xc003dec000}, {0xa405e70, 0xc002ebf180})\n\t/home/tim/Repositories/zitadel/zitadel/internal/api/grpc/server/connect_middleware/access_interceptor.go:21 +0x814\nconnectrpc.com/connect.unaryThunk.func1({0xa3c1410, 0xc003dec000}, {0xa405e70, 0xc002ebf180})\n\t/home/tim/go/pkg/mod/connectrpc.com/[email protected].1/interceptor.go:120 +0xd9\ngithub.com/zitadel/zitadel/internal/api/grpc/server/connect_middleware.addInstanceByRequestedHost({0xa3c1410, 0xc003db1110}, {0xa405e70, 0xc002ebf180}, 0xc00321c090, {0xa3a63e8, 0xc0002f4a00}, 0xc002dee9b0, {0xc0012106a0, 0x9})\n\t/home/tim/Repositories/zitadel/zitadel/internal/api/grpc/server/connect_middleware/instance_interceptor.go:107 +0xbc3\ngithub.com/zitadel/zitadel/internal/api/grpc/server/connect_middleware.setInstance({0xa3c1410, 0xc003db10e0}, {0xa405e70, 0xc002ebf180}, 0xc00321c090, {0xa3a63e8, 0xc0002f4a00}, {0xc0012106a0, 0x9}, 0xc002dee9b0, ...)\n\t/home/tim/Repositories/zitadel/zitadel/internal/api/grpc/server/connect_middleware/instance_interceptor.go:61 +0xb05\ngithub.com/zitadel/zitadel/internal/api/grpc/server/connect_middleware.InstanceInterceptor.func1.1({0xa3c1410, 0xc003db10e0}, {0xa405e70, 0xc002ebf180})\n\t/home/tim/Repositories/zitadel/zitadel/internal/api/grpc/server/connect_middleware/instance_interceptor.go:23 +0x147\nconnectrpc.com/connect.unaryThunk.func1({0xa3c1410, 0xc003db10e0}, {0xa405e70, 0xc002ebf180})\n\t/home/tim/go/pkg/mod/connectrpc.com/[email protected].1/interceptor.go:120 +0xd9\ngithub.com/zitadel/zitadel/internal/api/grpc/server/connect_middleware.NoCacheInterceptor.func1.1({0xa3c1410, 0xc003db10e0}, {0xa405e70, 0xc002ebf180})\n\t/home/tim/Repositories/zitadel/zitadel/internal/api/grpc/server/connect_middleware/cache_interceptor.go:21 +0x351\nconnectrpc.com/connect.unaryThunk.func1({0xa3c1410, 0xc003db10e0}, {0xa405e70, 0xc002ebf180})\n\t/home/tim/go/pkg/mod/connectrpc.com/[email protected].1/interceptor.go:120 +0xd9\ngithub.com/zitadel/zitadel/backend/v3/instrumentation/logging.NewConnectInterceptor.func1({0xa3c1410, 0xc003db10e0}, {0xa405e70, 0xc002ebf180})\n\t/home/tim/Repositories/zitadel/zitadel/backend/v3/instrumentation/logging/connect_handler.go:26 +0x27b\nconnectrpc.com/connect.unaryThunk.func1({0xa3c1410, 0xc003db1050}, {0xa405e70, 0xc002ebf180})\n\t/home/tim/go/pkg/mod/connectrpc.com/[email protected].1/interceptor.go:120 +0xd9\ngithub.com/zitadel/zitadel/internal/api/grpc/server/connect_middleware.RegisterMetrics({0xa3c1410, 0xc003db1050}, {0xa405e70, 0xc002ebf180}, 0xc00321c0d0, {0xcf754f8, 0x3, 0x3}, {0xc0008b8840, 0x4, ...})\n\t/home/tim/Repositories/zitadel/zitadel/internal/api/grpc/server/connect_middleware/metrics_interceptor.go:47 +0x3f3\ngithub.com/zitadel/zitadel/internal/api/grpc/server/connect_middleware.MetricsHandler.func1.1({0xa3c1410, 0xc003db1050}, {0xa405e70, 0xc002ebf180})\n\t/home/tim/Repositories/zitadel/zitadel/internal/api/grpc/server/connect_middleware/metrics_interceptor.go:31 +0x111\nconnectrpc.com/connect.unaryThunk.func1({0xa3c1410, 0xc003db1050}, {0xa405e70, 0xc002ebf180})\n\t/home/tim/go/pkg/mod/connectrpc.com/[email protected].1/interceptor.go:120 +0xd9\nconnectrpc.com/otelconnect.(*Interceptor).WrapUnary.func1({0xa3c1410, 0xc003db1050}, {0xa405e70, 0xc002ebf180})\n\t/home/tim/go/pkg/mod/connectrpc.com/[email protected]/interceptor.go:145 +0x16d7\nconnectrpc.com/connect.unaryThunk.func1({0xa3c1410, 0xc003db0ff0}, {0xa405e70, 0xc002ebf180})\n\t/home/tim/go/pkg/mod/connectrpc.com/[email protected].1/interceptor.go:120 +0xd9\ngithub.com/zitadel/zitadel/internal/api/grpc/server/connect_middleware.CallDurationHandler.func1.1({0xa3c1410, 0xc003db0ff0}, {0xa405e70, 0xc002ebf180})\n\t/home/tim/Repositories/zitadel/zitadel/internal/api/grpc/server/connect_middleware/call_interceptor.go:15 +0xab\nconnectrpc.com/connect.NewUnaryHandler[...].func2({0x7f11083fe700, 0xc000503a40})\n\t/home/tim/go/pkg/mod/connectrpc.com/[email protected].1/handler.go:78 +0x4e2\nconnectrpc.com/connect.(*Handler).ServeHTTP(0xc0004dd420, {0xa3bb420, 0xc0006b22a0}, 0xc002e3b2c0)\n\t/home/tim/go/pkg/mod/connectrpc.com/[email protected].1/handler.go:333 +0x870\ngithub.com/zitadel/zitadel/pkg/grpc/user/v2/userconnect.NewUserServiceHandler.func1({0xa3bb420, 0xc0006b22a0}, 0xc002e3b2c0)\n\t/home/tim/Repositories/zitadel/zitadel/pkg/grpc/user/v2/userconnect/user_service.connect.go:1951 +0x8e5\nnet/http.HandlerFunc.ServeHTTP(0xc002d7a000, {0xa3bb420, 0xc0006b22a0}, 0xc002e3b2c0)\n\t/usr/lib/go/src/net/http/server.go:2322 +0x33\ngithub.com/rs/cors.(*Cors).Handler.func1({0xa3bb420, 0xc0006b22a0}, 0xc002e3b2c0)\n\t/home/tim/go/pkg/mod/github.com/rs/[email protected].1/cors.go:289 +0x2fd\nnet/http.HandlerFunc.ServeHTTP(0xc000191aa0, {0xa3bb420, 0xc0006b22a0}, 0xc002e3b2c0)\n\t/usr/lib/go/src/net/http/server.go:2322 +0x33\ngithub.com/zitadel/zitadel/internal/api/http/middleware.RobotsTagHandler.func1({0xa3bb420, 0xc0006b22a0}, 0xc002e3b2c0)\n\t/home/tim/Repositories/zitadel/zitadel/internal/api/http/middleware/robots_tag_interceptor.go:12 +0x88\nnet/http.HandlerFunc.ServeHTTP(0xc002e14798, {0xa3bb420, 0xc0006b22a0}, 0xc002e3b2c0)\n\t/usr/lib/go/src/net/http/server.go:2322 +0x33\ngithub.com/zitadel/zitadel/internal/api/http/middleware.WithOrigin.func1.1({0xa3bb420, 0xc0006b22a0}, 0xc002e3b180)\n\t/home/tim/Repositories/zitadel/zitadel/internal/api/http/middleware/origin_interceptor.go:27 +0x42a\nnet/http.HandlerFunc.ServeHTTP(0xc003d89a40, {0xa3bb420, 0xc0006b22a0}, 0xc002e3b180)\n\t/usr/lib/go/src/net/http/server.go:2322 +0x33\ngithub.com/gorilla/mux.(*Router).ServeHTTP(0xc002dfa840, {0xa3bb420, 0xc0006b22a0}, 0xc002e3b180)\n\t/home/tim/go/pkg/mod/github.com/gorilla/[email protected]/mux.go:212 +0x2bb\ngolang.org/x/net/http2.(*serverConn).runHandler(0xc003e143c0, 0xc0006b22a0, 0xc0002f4000, 0xc002d9ae88)\n\t/home/tim/go/pkg/mod/golang.org/x/[email protected].0/http2/server.go:2424 +0x1b9\ncreated by golang.org/x/net/http2.(*serverConn).scheduleHandler in goroutine 607\n\t/home/tim/go/pkg/mod/golang.org/x/[email protected].0/http2/server.go:2359 +0x1df\n"
  }
}
```

</details>

When the GCP error reporting handler is enabled with stack trace, as per
[formatting
requirements](https://docs.cloud.google.com/error-reporting/docs/formatting-error-messages):
- A `@type` field is provided
- Some fields are renamed according to Google Cloud Logging specs.
(severity, message etc)
- The stack strace is appended to the `message` field.
- The report location is moved into the top-level `reportLocation`
field.

The original error is still logged in the `error` field.
This is not part of the error reporting API but may still be useful for
logging.

<details>

<summary>GCP error report with stack trace</summary>

```json
{
  "@type": "type.googleapis.com/google.devtools.clouderrorreporting.v1beta1.ReportedErrorEvent",
  "SpanID": "4fdeae9817ade4f5",
  "TraceID": "78e31366d4c36e0718a2dcb6ca73d2f3",
  "domain": { "instance_host": "localhost:8080", "protocol": "http" },
  "duration": "82.464896ms",
  "error": {
    "id": "COMMAND-bd4ir1mblj",
    "kind": "NotFound",
    "message": "User could not be found"
  },
  "http_method": "POST",
  "logging.googleapis.com/sourceLocation": {
    "function": "github.com/zitadel/zitadel/internal/api/grpc/gerrors.ZITADELToConnectError",
    "file": "/home/tim/Repositories/zitadel/zitadel/internal/api/grpc/gerrors/zitadel_errors.go",
    "line": 57
  },
  "message": "ID=COMMAND-bd4ir1mblj Message=User could not be found\ngoroutine 1165 [running]:\nruntime/debug.Stack()\n\t/usr/lib/go/src/runtime/debug/stack.go:26 +0x8e\ngithub.com/zitadel/zitadel/internal/zerrors.newZitadelError(0x5, {0x0, 0x0}, {0x6af7719, 0x12}, {0x6aff994, 0x14})\n\t/home/tim/Repositories/zitadel/zitadel/internal/zerrors/zerror.go:139 +0x1df\ngithub.com/zitadel/zitadel/internal/zerrors.ThrowNotFound({0x0, 0x0}, {0x6af7719, 0x12}, {0x6aff994, 0x14})\n\t/home/tim/Repositories/zitadel/zitadel/internal/zerrors/not_found.go:6 +0x70\ngithub.com/zitadel/zitadel/internal/command.(*Commands).RemoveUserV2(0xc000498588, {0xa3c1450, 0xc002cba540}, {0xc003030910, 0xb}, {0x0, 0x0}, {0xd550a80, 0x0, 0x0}, ...)\n\t/home/tim/Repositories/zitadel/zitadel/internal/command/user_v2.go:140 +0x711\ngithub.com/zitadel/zitadel/internal/api/grpc/user/v2.(*Server).DeleteUser(0xc003101500, {0xa3c1450, 0xc002cba540}, 0xc00216ec80)\n\t/home/tim/Repositories/zitadel/zitadel/internal/api/grpc/user/v2/user.go:191 +0x3f1\nconnectrpc.com/connect.NewUnaryHandler[...].func1({0xa405eb0, 0xc00216ec80})\n\t/home/tim/go/pkg/mod/connectrpc.com/[email protected].1/handler.go:51 +0x17e\nconnectrpc.com/connect.unaryThunk.func1({0xa3c1450, 0xc002cba540}, {0xa405eb0, 0xc00216ec80})\n\t/home/tim/go/pkg/mod/connectrpc.com/[email protected].1/interceptor.go:120 +0xd9\ngithub.com/zitadel/zitadel/internal/api/grpc/server/connect_middleware.ActivityInterceptor.func1.1({0xa3c1450, 0xc002cba540}, {0xa405eb0, 0xc00216ec80})\n\t/home/tim/Repositories/zitadel/zitadel/internal/api/grpc/server/connect_middleware/activity_interceptor.go:20 +0x1b1\nconnectrpc.com/connect.unaryThunk.func1({0xa3c1450, 0xc002cba330}, {0xa405eb0, 0xc00216ec80})\n\t/home/tim/go/pkg/mod/connectrpc.com/[email protected].1/interceptor.go:120 +0xd9\ngithub.com/zitadel/zitadel/internal/api/grpc/server/connect_middleware.ServiceHandler.func1.1({0xa3c1450, 0xc002cba330}, {0xa405eb0, 0xc00216ec80})\n\t/home/tim/Repositories/zitadel/zitadel/internal/api/grpc/server/connect_middleware/service_interceptor.go:22 +0x283\nconnectrpc.com/connect.unaryThunk.func1({0xa3c1450, 0xc002cba330}, {0xa405eb0, 0xc00216ec80})\n\t/home/tim/go/pkg/mod/connectrpc.com/[email protected].1/interceptor.go:120 +0xd9\ngithub.com/zitadel/zitadel/internal/api/grpc/server/connect_middleware.validate({0xa3c1450, 0xc002cba330}, {0xa405eb0, 0xc00216ec80}, 0xc003033180)\n\t/home/tim/Repositories/zitadel/zitadel/internal/api/grpc/server/connect_middleware/validation_interceptor.go:35 +0x1bd\ngithub.com/zitadel/zitadel/internal/api/grpc/server/connect_middleware.ValidationHandler.func1.1({0xa3c1450, 0xc002cba330}, {0xa405eb0, 0xc00216ec80})\n\t/home/tim/Repositories/zitadel/zitadel/internal/api/grpc/server/connect_middleware/validation_interceptor.go:15 +0x85\nconnectrpc.com/connect.unaryThunk.func1({0xa3c1450, 0xc002cba330}, {0xa405eb0, 0xc00216ec80})\n\t/home/tim/go/pkg/mod/connectrpc.com/[email protected].1/interceptor.go:120 +0xd9\ngithub.com/zitadel/zitadel/internal/api/grpc/server/connect_middleware.ExecutionHandler.func1.1({0xa3c1450, 0xc002cba330}, {0xa405eb0, 0xc00216ec80})\n\t/home/tim/Repositories/zitadel/zitadel/internal/api/grpc/server/connect_middleware/execution_interceptor.go:39 +0x376\nconnectrpc.com/connect.unaryThunk.func1({0xa3c1450, 0xc002cba330}, {0xa405eb0, 0xc00216ec80})\n\t/home/tim/go/pkg/mod/connectrpc.com/[email protected].1/interceptor.go:120 +0xd9\ngithub.com/zitadel/zitadel/internal/api/grpc/server/connect_middleware.QuotaExhaustedInterceptor.func1.1({0xa3c1450, 0xc002cba330}, {0xa405eb0, 0xc00216ec80})\n\t/home/tim/Repositories/zitadel/zitadel/internal/api/grpc/server/connect_middleware/quota_interceptor.go:25 +0x42d\nconnectrpc.com/connect.unaryThunk.func1({0xa3c1450, 0xc002cba330}, {0xa405eb0, 0xc00216ec80})\n\t/home/tim/go/pkg/mod/connectrpc.com/[email protected].1/interceptor.go:120 +0xd9\ngithub.com/zitadel/zitadel/internal/api/grpc/server/connect_middleware.TranslationHandler.func1.1({0xa3c1450, 0xc002cba330}, {0xa405eb0, 0xc00216ec80})\n\t/home/tim/Repositories/zitadel/zitadel/internal/api/grpc/server/connect_middleware/translation_interceptor.go:18 +0x94\nconnectrpc.com/connect.unaryThunk.func1({0xa3c1450, 0xc002cba330}, {0xa405eb0, 0xc00216ec80})\n\t/home/tim/go/pkg/mod/connectrpc.com/[email protected].1/interceptor.go:120 +0xd9\ngithub.com/zitadel/zitadel/internal/api/grpc/server/connect_middleware.authorize({0xa3c1450, 0xc0015827b0}, {0xa405eb0, 0xc00216ec80}, 0xc0030331e0, {0xa3f0ab0, 0xc000203f10}, {{0xc000865980, 0x9, 0x9}}, ...)\n\t/home/tim/Repositories/zitadel/zitadel/internal/api/grpc/server/connect_middleware/auth_interceptor.go:42 +0x894\ngithub.com/zitadel/zitadel/internal/api/grpc/server/connect_middleware.AuthorizationInterceptor.func1.1({0xa3c1450, 0xc0015827b0}, {0xa405eb0, 0xc00216ec80})\n\t/home/tim/Repositories/zitadel/zitadel/internal/api/grpc/server/connect_middleware/auth_interceptor.go:17 +0x151\nconnectrpc.com/connect.unaryThunk.func1({0xa3c1450, 0xc0015827b0}, {0xa405eb0, 0xc00216ec80})\n\t/home/tim/go/pkg/mod/connectrpc.com/[email protected].1/interceptor.go:120 +0xd9\ngithub.com/zitadel/zitadel/internal/api/grpc/server/connect_middleware.LimitsInterceptor.func1.1({0xa3c1450, 0xc0015827b0}, {0xa405eb0, 0xc00216ec80})\n\t/home/tim/Repositories/zitadel/zitadel/internal/api/grpc/server/connect_middleware/limits_interceptor.go:31 +0x3b7\nconnectrpc.com/connect.unaryThunk.func1({0xa3c1450, 0xc0015827b0}, {0xa405eb0, 0xc00216ec80})\n\t/home/tim/go/pkg/mod/connectrpc.com/[email protected].1/interceptor.go:120 +0xd9\ngithub.com/zitadel/zitadel/internal/api/grpc/server/connect_middleware.toConnectError({0xa3c1450, 0xc0015827b0}, {0xa405eb0, 0xc00216ec80}, 0xc003033200)\n\t/home/tim/Repositories/zitadel/zitadel/internal/api/grpc/server/connect_middleware/error_interceptor.go:21 +0x8a\ngithub.com/zitadel/zitadel/internal/api/grpc/server/connect_middleware.ErrorHandler.func1.1({0xa3c1450, 0xc0015827b0}, {0xa405eb0, 0xc00216ec80})\n\t/home/tim/Repositories/zitadel/zitadel/internal/api/grpc/server/connect_middleware/error_interceptor.go:15 +0x85\nconnectrpc.com/connect.unaryThunk.func1({0xa3c1450, 0xc0015827b0}, {0xa405eb0, 0xc00216ec80})\n\t/home/tim/go/pkg/mod/connectrpc.com/[email protected].1/interceptor.go:120 +0xd9\ngithub.com/zitadel/zitadel/internal/api/grpc/server/connect_middleware.AccessStorageInterceptor.func1.1({0xa3c1450, 0xc0015827b0}, {0xa405eb0, 0xc00216ec80})\n\t/home/tim/Repositories/zitadel/zitadel/internal/api/grpc/server/connect_middleware/access_interceptor.go:21 +0x814\nconnectrpc.com/connect.unaryThunk.func1({0xa3c1450, 0xc0015827b0}, {0xa405eb0, 0xc00216ec80})\n\t/home/tim/go/pkg/mod/connectrpc.com/[email protected].1/interceptor.go:120 +0xd9\ngithub.com/zitadel/zitadel/internal/api/grpc/server/connect_middleware.addInstanceByRequestedHost({0xa3c1450, 0xc001636630}, {0xa405eb0, 0xc00216ec80}, 0xc003033230, {0xa3a6428, 0xc00069f040}, 0xc002076910, {0xc002cef510, 0x9})\n\t/home/tim/Repositories/zitadel/zitadel/internal/api/grpc/server/connect_middleware/instance_interceptor.go:107 +0xbc3\ngithub.com/zitadel/zitadel/internal/api/grpc/server/connect_middleware.setInstance({0xa3c1450, 0xc0016365a0}, {0xa405eb0, 0xc00216ec80}, 0xc003033230, {0xa3a6428, 0xc00069f040}, {0xc002cef510, 0x9}, 0xc002076910, ...)\n\t/home/tim/Repositories/zitadel/zitadel/internal/api/grpc/server/connect_middleware/instance_interceptor.go:61 +0xb05\ngithub.com/zitadel/zitadel/internal/api/grpc/server/connect_middleware.InstanceInterceptor.func1.1({0xa3c1450, 0xc0016365a0}, {0xa405eb0, 0xc00216ec80})\n\t/home/tim/Repositories/zitadel/zitadel/internal/api/grpc/server/connect_middleware/instance_interceptor.go:23 +0x147\nconnectrpc.com/connect.unaryThunk.func1({0xa3c1450, 0xc0016365a0}, {0xa405eb0, 0xc00216ec80})\n\t/home/tim/go/pkg/mod/connectrpc.com/[email protected].1/interceptor.go:120 +0xd9\ngithub.com/zitadel/zitadel/internal/api/grpc/server/connect_middleware.NoCacheInterceptor.func1.1({0xa3c1450, 0xc0016365a0}, {0xa405eb0, 0xc00216ec80})\n\t/home/tim/Repositories/zitadel/zitadel/internal/api/grpc/server/connect_middleware/cache_interceptor.go:21 +0x351\nconnectrpc.com/connect.unaryThunk.func1({0xa3c1450, 0xc0016365a0}, {0xa405eb0, 0xc00216ec80})\n\t/home/tim/go/pkg/mod/connectrpc.com/[email protected].1/interceptor.go:120 +0xd9\ngithub.com/zitadel/zitadel/backend/v3/instrumentation/logging.NewConnectInterceptor.func1({0xa3c1450, 0xc0016365a0}, {0xa405eb0, 0xc00216ec80})\n\t/home/tim/Repositories/zitadel/zitadel/backend/v3/instrumentation/logging/connect_handler.go:26 +0x27b\nconnectrpc.com/connect.unaryThunk.func1({0xa3c1450, 0xc0016364e0}, {0xa405eb0, 0xc00216ec80})\n\t/home/tim/go/pkg/mod/connectrpc.com/[email protected].1/interceptor.go:120 +0xd9\ngithub.com/zitadel/zitadel/internal/api/grpc/server/connect_middleware.RegisterMetrics({0xa3c1450, 0xc0016364e0}, {0xa405eb0, 0xc00216ec80}, 0xc003033270, {0xcf754f8, 0x3, 0x3}, {0xc000530f60, 0x4, ...})\n\t/home/tim/Repositories/zitadel/zitadel/internal/api/grpc/server/connect_middleware/metrics_interceptor.go:47 +0x3f3\ngithub.com/zitadel/zitadel/internal/api/grpc/server/connect_middleware.MetricsHandler.func1.1({0xa3c1450, 0xc0016364e0}, {0xa405eb0, 0xc00216ec80})\n\t/home/tim/Repositories/zitadel/zitadel/internal/api/grpc/server/connect_middleware/metrics_interceptor.go:31 +0x111\nconnectrpc.com/connect.unaryThunk.func1({0xa3c1450, 0xc0016364e0}, {0xa405eb0, 0xc00216ec80})\n\t/home/tim/go/pkg/mod/connectrpc.com/[email protected].1/interceptor.go:120 +0xd9\nconnectrpc.com/otelconnect.(*Interceptor).WrapUnary.func1({0xa3c1450, 0xc0016364e0}, {0xa405eb0, 0xc00216ec80})\n\t/home/tim/go/pkg/mod/connectrpc.com/[email protected]/interceptor.go:145 +0x16d7\nconnectrpc.com/connect.unaryThunk.func1({0xa3c1450, 0xc001636450}, {0xa405eb0, 0xc00216ec80})\n\t/home/tim/go/pkg/mod/connectrpc.com/[email protected].1/interceptor.go:120 +0xd9\ngithub.com/zitadel/zitadel/internal/api/grpc/server/connect_middleware.CallDurationHandler.func1.1({0xa3c1450, 0xc001636450}, {0xa405eb0, 0xc00216ec80})\n\t/home/tim/Repositories/zitadel/zitadel/internal/api/grpc/server/connect_middleware/call_interceptor.go:15 +0xab\nconnectrpc.com/connect.NewUnaryHandler[...].func2({0x7fb6100a8e60, 0xc002fa5680})\n\t/home/tim/go/pkg/mod/connectrpc.com/[email protected].1/handler.go:78 +0x4e2\nconnectrpc.com/connect.(*Handler).ServeHTTP(0xc0040768c0, {0xa3bb460, 0xc0025bf360}, 0xc0024c23c0)\n\t/home/tim/go/pkg/mod/connectrpc.com/[email protected].1/handler.go:333 +0x870\ngithub.com/zitadel/zitadel/pkg/grpc/user/v2/userconnect.NewUserServiceHandler.func1({0xa3bb460, 0xc0025bf360}, 0xc0024c23c0)\n\t/home/tim/Repositories/zitadel/zitadel/pkg/grpc/user/v2/userconnect/user_service.connect.go:1951 +0x8e5\nnet/http.HandlerFunc.ServeHTTP(0xc00314a200, {0xa3bb460, 0xc0025bf360}, 0xc0024c23c0)\n\t/usr/lib/go/src/net/http/server.go:2322 +0x33\ngithub.com/rs/cors.(*Cors).Handler.func1({0xa3bb460, 0xc0025bf360}, 0xc0024c23c0)\n\t/home/tim/go/pkg/mod/github.com/rs/[email protected].1/cors.go:289 +0x2fd\nnet/http.HandlerFunc.ServeHTTP(0xc0022cbdc0, {0xa3bb460, 0xc0025bf360}, 0xc0024c23c0)\n\t/usr/lib/go/src/net/http/server.go:2322 +0x33\ngithub.com/zitadel/zitadel/internal/api/http/middleware.RobotsTagHandler.func1({0xa3bb460, 0xc0025bf360}, 0xc0024c23c0)\n\t/home/tim/Repositories/zitadel/zitadel/internal/api/http/middleware/robots_tag_interceptor.go:12 +0x88\nnet/http.HandlerFunc.ServeHTTP(0xc001c8fae8, {0xa3bb460, 0xc0025bf360}, 0xc0024c23c0)\n\t/usr/lib/go/src/net/http/server.go:2322 +0x33\ngithub.com/zitadel/zitadel/internal/api/http/middleware.WithOrigin.func1.1({0xa3bb460, 0xc0025bf360}, 0xc0024c2140)\n\t/home/tim/Repositories/zitadel/zitadel/internal/api/http/middleware/origin_interceptor.go:27 +0x42a\nnet/http.HandlerFunc.ServeHTTP(0xc00048e540, {0xa3bb460, 0xc0025bf360}, 0xc0024c2140)\n\t/usr/lib/go/src/net/http/server.go:2322 +0x33\ngithub.com/gorilla/mux.(*Router).ServeHTTP(0xc00207c540, {0xa3bb460, 0xc0025bf360}, 0xc0024c2140)\n\t/home/tim/go/pkg/mod/github.com/gorilla/[email protected]/mux.go:212 +0x2bb\ngolang.org/x/net/http2.(*serverConn).runHandler(0xc0025545a0, 0xc0025bf360, 0xc0023fd180, 0xc001703488)\n\t/home/tim/go/pkg/mod/golang.org/x/[email protected].0/http2/server.go:2424 +0x1b9\ncreated by golang.org/x/net/http2.(*serverConn).scheduleHandler in goroutine 620\n\t/home/tim/go/pkg/mod/golang.org/x/[email protected].0/http2/server.go:2359 +0x1df\n",
  "path": "/zitadel.user.v2.UserService/DeleteUser",
  "protocol": "connect",
  "reportLocation": {
    "filePath": "/home/tim/Repositories/zitadel/zitadel/internal/command/user_v2.go",
    "lineNumber": 140,
    "functionName": "github.com/zitadel/zitadel/internal/command.(*Commands).RemoveUserV2"
  },
  "request_id": "d5kgsu8edncaon6puvag",
  "service": "zitadel.user.v2.UserService",
  "severity": "WARNING",
  "time": "2026-01-15T16:57:45.341000592+01:00"
}
```

</details>

When the GCP error reporting handler is enabled without stack trace,
the `message` field contains the error string, also as per formatting
requirements.

<details>

<summary>GCP error report without stack trace</summary>

```json
{
  "@type": "type.googleapis.com/google.devtools.clouderrorreporting.v1beta1.ReportedErrorEvent",
  "SpanID": "2b4157f874eddbf4",
  "TraceID": "c34f7404fc0d021e1868ccc687bf2995",
  "domain": { "instance_host": "localhost:8080", "protocol": "http" },
  "duration": "52.061597ms",
  "error": {
    "id": "COMMAND-bd4ir1mblj",
    "kind": "NotFound",
    "message": "User could not be found"
  },
  "http_method": "POST",
  "logging.googleapis.com/sourceLocation": {
    "function": "github.com/zitadel/zitadel/internal/api/grpc/gerrors.ZITADELToConnectError",
    "file": "/home/tim/Repositories/zitadel/zitadel/internal/api/grpc/gerrors/zitadel_errors.go",
    "line": 57
  },
  "message": "ID=COMMAND-bd4ir1mblj Message=User could not be found",
  "path": "/zitadel.user.v2.UserService/DeleteUser",
  "protocol": "connect",
  "reportLocation": {
    "filePath": "/home/tim/Repositories/zitadel/zitadel/internal/command/user_v2.go",
    "lineNumber": 140,
    "functionName": "github.com/zitadel/zitadel/internal/command.(*Commands).RemoveUserV2"
  },
  "request_id": "d5kf5tgedncaiajvls9g",
  "service": "zitadel.user.v2.UserService",
  "severity": "WARNING",
  "time": "2026-01-15T15:00:22.910899273+01:00"
}
```

</details>

# Additional Changes

- Private constructor for zitadel errors so that the stack-depth is
consistent for different ways of error creation. (Throw and Create
variants)
- Request logs are now always at info level.
- Bump Go version 1.25, required for `sloggcp`

# Additional Context

- closes #11329

---------

Co-authored-by: Copilot <[email protected]>

internal/zerrors/zerror.go

@@ -4,6 +4,10 @@ import (
 	"errors"
 	"fmt"
 	"log/slog"
+	"runtime/debug"
+	"sync/atomic"
+
+	"github.com/zitadel/sloggcp"
 )
 
 //go:generate enumer -type=Kind -trimprefix=Kind -json
@@ -76,24 +80,66 @@ const (
 	KindUnauthenticated Kind = 16
 )
 
+// Because errors are created through singletons, config is global.
+var (
+	enableReportLocation atomic.Bool
+	enableStackTrace     atomic.Bool
+	gcpErrorReporting    atomic.Bool
+)
+
+// EnableReportLocation enables or disables report locations for created errors.
+func EnableReportLocation(enable bool) {
+	enableReportLocation.Store(enable)
+}
+
+// EnableStackTrace enables or disables stack traces for created errors.
+func EnableStackTrace(enable bool) {
+	enableStackTrace.Store(enable)
+}
+
+// GCPErrorReportingEnabled enables or disables special handling for GCP Error Reporting.
+// It must be enabled when using a sloggcp handler to avoid duplicate report locations and stack traces.
+func GCPErrorReportingEnabled(enable bool) {
+	gcpErrorReporting.Store(enable)
+}
+
 type ZitadelError struct {
 	Kind    Kind
 	Parent  error
 	Message string
 	ID      string
+
+	// location where the error was created
+	reportLocation *sloggcp.ReportLocation
+	// stack trace at the point the error was created
+	stackTrace    []byte
+	hasStackTrace bool
 }
 
 func ThrowError(parent error, id, message string) error {
-	return CreateZitadelError(KindUnknown, parent, id, message)
+	return newZitadelError(KindUnknown, parent, id, message)
 }
 
 func CreateZitadelError(kind Kind, parent error, id, message string) *ZitadelError {
-	return &ZitadelError{
+	return newZitadelError(kind, parent, id, message)
+}
+
+func newZitadelError(kind Kind, parent error, id, message string) *ZitadelError {
+	err := &ZitadelError{
 		Kind:    kind,
 		Parent:  parent,
 		ID:      id,
 		Message: message,
 	}
+	if enableReportLocation.Load() {
+		// skip 2: newZitadelError + Create / Throw function.
+		err.reportLocation = sloggcp.NewReportLocation(2)
+	}
+	if enableStackTrace.Load() {
+		err.stackTrace = debug.Stack()
+		err.hasStackTrace = true
+	}
+	return err
 }
 
 func (err *ZitadelError) Error() string {
@@ -158,10 +204,41 @@ func AsZitadelError(err error) (*ZitadelError, bool) {
 var _ slog.LogValuer = (*ZitadelError)(nil)
 
 func (err *ZitadelError) LogValue() slog.Value {
-	return slog.GroupValue(
+	attributes := make([]slog.Attr, 0, 6)
+	attributes = append(attributes,
 		slog.String("kind", err.Kind.String()),
 		slog.String("message", err.Message),
 		slog.String("id", err.ID),
-		slog.Any("parent", err.Parent),
 	)
+	if err.Parent != nil {
+		attributes = append(attributes, slog.Any("parent", err.Parent))
+	}
+	// if gcp error reporting is enabled, log the error as a group without
+	// report location and stack trace, as those are handled by the handler.
+	if gcpErrorReporting.Load() {
+		return slog.GroupValue(attributes...)
+	}
+
+	if err.reportLocation != nil {
+		attributes = append(attributes, slog.Any("reportLocation", err.reportLocation))
+	}
+	if err.hasStackTrace {
+		attributes = append(attributes, slog.String("stackTrace", string(err.stackTrace)))
+	}
+	return slog.GroupValue(attributes...)
 }
+
+// ReportLocation implements [sloggcp.ReportLocationError].
+func (err *ZitadelError) ReportLocation() *sloggcp.ReportLocation {
+	return err.reportLocation
+}
+
+// StackTrace implements [sloggcp.StackTraceError].
+func (err *ZitadelError) StackTrace() (trace []byte, ok bool) {
+	return err.stackTrace, err.hasStackTrace
+}
+
+var (
+	_ sloggcp.ReportLocationError = (*ZitadelError)(nil)
+	_ sloggcp.StackTraceError     = (*ZitadelError)(nil)
+)