feat: Add structured logging with logrus and configurable output formats

- Add sirupsen/logrus v1.9.4 dependency to go.mod
- Add logging package with global Logger instance
- Add Config struct with Level, Format, and Output fields
- Add DefaultConfig with LOG_LEVEL, LOG_FORMAT, and LOG_OUTPUT environment variables
- Add Init function with level parsing, JSON/text formatter selection, and stdout/stderr output
- Add InitWithDefaults helper function
- Add WithField, WithFields, and WithError helper

apps/api-server/go.mod

@@ -154,6 +154,7 @@ require (
 	github.com/quic-go/qpack v0.6.0 // indirect
 	github.com/quic-go/quic-go v0.59.0 // indirect
 	github.com/rabbitmq/amqp091-go v1.11.0
+	github.com/sirupsen/logrus v1.9.4
 	github.com/stripe/stripe-go/v82 v82.5.1
 	github.com/twitchyliquid64/golang-asm v0.15.1 // indirect
 	github.com/ugorji/go/codec v1.3.1 // indirect

apps/api-server/go.sum

@@ -391,6 +391,8 @@ github.com/shopspring/decimal v1.4.0 h1:bxl37RwXBklmTi0C79JfXCEBD1cqqHt0bbgBAGFp
 github.com/shopspring/decimal v1.4.0/go.mod h1:gawqmDU56v4yIKSwfBSFip1HdCCXN8/+DMd9qYNcwME=
 github.com/sirupsen/logrus v1.2.0/go.mod h1:LxeOpSwHxABJmUn/MG1IvRgCAasNZTLOkJPxbbu5VWo=
 github.com/sirupsen/logrus v1.4.2/go.mod h1:tLMulIdttU9McNUspp0xgXVQah82FyeX6MwdIuYE2rE=
+github.com/sirupsen/logrus v1.9.4 h1:TsZE7l11zFCLZnZ+teH4Umoq5BhEIfIzfRDZ1Uzql2w=
+github.com/sirupsen/logrus v1.9.4/go.mod h1:ftWc9WdOfJ0a92nsE2jF5u5ZwH8Bv2zdeOC42RjbV2g=
 github.com/sosodev/duration v1.4.0 h1:35ed0KiVFriGHHzZZJaZLgmTEEICIyt8Sx0RQfj9IjE=
 github.com/sosodev/duration v1.4.0/go.mod h1:RQIBBX0+fMLc/D9+Jb/fwvVmo0eZvDDEERAikUR6SDg=
 github.com/spf13/pflag v1.0.10 h1:4EBh2KAYBwaONj6b2Ye1GiHfwjqyROoF4RwYO+vPwFk=

apps/api-server/internal/logging/logging.go

@@ -0,0 +1,141 @@
+package logging
+
+import (
+	"os"
+	"time"
+
+	"github.com/sirupsen/logrus"
+)
+
+var Logger *logrus.Logger
+
+// Config holds logging configuration
+type Config struct {
+	Level    string
+	Format   string // "json" or "text"
+	Output   string // "stdout" or "stderr"
+}
+
+// DefaultConfig returns default logging configuration
+func DefaultConfig() Config {
+	return Config{
+		Level:  os.Getenv("LOG_LEVEL"),
+		Format: os.Getenv("LOG_FORMAT"),
+		Output: os.Getenv("LOG_OUTPUT"),
+	}
+}
+
+// Init initializes the global logger with the given configuration
+func Init(config Config) error {
+	Logger = logrus.New()
+
+	// Set log level
+	if config.Level == "" {
+		config.Level = "info"
+	}
+	level, err := logrus.ParseLevel(config.Level)
+	if err != nil {
+		level = logrus.InfoLevel
+	}
+	Logger.SetLevel(level)
+
+	// Set log format
+	if config.Format == "" {
+		config.Format = "json"
+	}
+	if config.Format == "json" {
+		Logger.SetFormatter(&logrus.JSONFormatter{
+			TimestampFormat: time.RFC3339,
+			FieldMap: logrus.FieldMap{
+				logrus.FieldKeyTime:  "timestamp",
+				logrus.FieldKeyLevel: "level",
+				logrus.FieldKeyMsg:   "message",
+				logrus.FieldKeyFunc:  "function",
+			},
+		})
+	} else {
+		Logger.SetFormatter(&logrus.TextFormatter{
+			TimestampFormat: time.RFC3339,
+			FullTimestamp:   true,
+		})
+	}
+
+	// Set output
+	if config.Output == "" || config.Output == "stdout" {
+		Logger.SetOutput(os.Stdout)
+	} else {
+		Logger.SetOutput(os.Stderr)
+	}
+
+	return nil
+}
+
+// InitWithDefaults initializes the global logger with default configuration
+func InitWithDefaults() error {
+	return Init(DefaultConfig())
+}
+
+// WithField returns a logger with a single field
+func WithField(key string, value interface{}) *logrus.Entry {
+	return Logger.WithField(key, value)
+}
+
+// WithFields returns a logger with multiple fields
+func WithFields(fields logrus.Fields) *logrus.Entry {
+	return Logger.WithFields(fields)
+}
+
+// WithError returns a logger with an error field
+func WithError(err error) *logrus.Entry {
+	return Logger.WithError(err)
+}
+
+// Info logs an info message
+func Info(args ...interface{}) {
+	Logger.Info(args...)
+}
+
+// Infof logs a formatted info message
+func Infof(format string, args ...interface{}) {
+	Logger.Infof(format, args...)
+}
+
+// Warn logs a warning message
+func Warn(args ...interface{}) {
+	Logger.Warn(args...)
+}
+
+// Warnf logs a formatted warning message
+func Warnf(format string, args ...interface{}) {
+	Logger.Warnf(format, args...)
+}
+
+// Error logs an error message
+func Error(args ...interface{}) {
+	Logger.Error(args...)
+}
+
+// Errorf logs a formatted error message
+func Errorf(format string, args ...interface{}) {
+	Logger.Errorf(format, args...)
+}
+
+// Fatal logs a fatal message and exits
+func Fatal(args ...interface{}) {
+	Logger.Fatal(args...)
+}
+
+// Fatalf logs a formatted fatal message and exits
+func Fatalf(format string, args ...interface{}) {
+	Logger.Fatalf(format, args...)
+}
+
+// Debug logs a debug message
+func Debug(args ...interface{}) {
+	Logger.Debug(args...)
+}
+
+// Debugf logs a formatted debug message
+func Debugf(format string, args ...interface{}) {
+	Logger.Debugf(format, args...)
+}