perf(actionsv2): execution target router (#10564)

# Which Problems Are Solved

The event execution system currently uses a projection handler that
subscribes to and processes all events for all instances. This creates a
high static cost because the system over-fetches event data, handling
many events that are not needed by most instances. This inefficiency is
also reflected in high "rows returned" metrics in the database.

# How the Problems Are Solved

Eliminate the use of a project handler. Instead, events for which
"execution targets" are defined, are directly pushed to the queue by the
eventstore. A Router is populated in the Instance object in the authz
middleware.

- By joining the execution targets to the instance, no additional
queries are needed anymore.
- As part of the instance object, execution targets are now cached as
well.
- Events are queued within the same transaction, giving transactional
guarantees on delivery.
- Uses the "insert many fast` variant of River. Multiple jobs are queued
in a single round-trip to the database.
- Fix compatibility with PostgreSQL 15

# Additional Changes

- The signing key was stored as plain-text in the river job payload in
the DB. This violated our [Secrets
Storage](https://zitadel.com/docs/concepts/architecture/secrets#secrets-storage)
principle. This change removed the field and only uses the encrypted
version of the signing key.
- Fixed the target ordering from descending to ascending.
- Some minor linter warnings on the use of `io.WriteString()`.

# Additional Context

- Introduced in https://github.com/zitadel/zitadel/pull/9249
- Closes https://github.com/zitadel/zitadel/issues/10553
- Closes https://github.com/zitadel/zitadel/issues/9832
- Closes https://github.com/zitadel/zitadel/issues/10372
- Closes https://github.com/zitadel/zitadel/issues/10492

---------

Co-authored-by: Stefan Benz <[email protected]>

internal/api/authz/instance.go

@@ -6,6 +6,7 @@ import (
 
 	"golang.org/x/text/language"
 
+	"github.com/zitadel/zitadel/internal/execution/target"
 	"github.com/zitadel/zitadel/internal/feature"
 )
 
@@ -23,6 +24,7 @@ type Instance interface {
 	Block() *bool
 	AuditLogRetention() *time.Duration
 	Features() feature.Features
+	ExecutionRouter() target.Router
 }
 
 type InstanceVerifier interface {
@@ -31,13 +33,14 @@ type InstanceVerifier interface {
 }
 
 type instance struct {
-	id              string
-	projectID       string
-	appID           string
-	clientID        string
-	orgID           string
-	defaultLanguage language.Tag
-	features        feature.Features
+	id               string
+	projectID        string
+	appID            string
+	clientID         string
+	orgID            string
+	defaultLanguage  language.Tag
+	features         feature.Features
+	executionTargets target.Router
 }
 
 func (i *instance) Block() *bool {
@@ -84,6 +87,10 @@ func (i *instance) Features() feature.Features {
 	return i.features
 }
 
+func (i *instance) ExecutionRouter() target.Router {
+	return i.executionTargets
+}
+
 func GetInstance(ctx context.Context) Instance {
 	instance, ok := ctx.Value(instanceKey).(Instance)
 	if !ok {
@@ -142,3 +149,12 @@ func WithFeatures(ctx context.Context, f feature.Features) context.Context {
 	i.features = f
 	return context.WithValue(ctx, instanceKey, i)
 }
+
+func WithExecutionRouter(ctx context.Context, router target.Router) context.Context {
+	i, ok := ctx.Value(instanceKey).(*instance)
+	if !ok {
+		i = new(instance)
+	}
+	i.executionTargets = router
+	return context.WithValue(ctx, instanceKey, i)
+}