feat(gl): add structured grpc observability

infrastructure/observability/logger.go

@@ -0,0 +1,30 @@
+package observability
+
+import (
+	"log/slog"
+	"os"
+)
+
+// Configure installs the process-wide JSON logger used by every GL adapter.
+func Configure(service string, level slog.Leveler) *slog.Logger {
+	handler := slog.NewJSONHandler(os.Stderr, &slog.HandlerOptions{
+		AddSource: true,
+		Level:     level,
+		ReplaceAttr: func(_ []string, attr slog.Attr) slog.Attr {
+			switch attr.Key {
+			case slog.TimeKey:
+				attr.Key = "timestamp"
+			case slog.LevelKey:
+				attr.Key = "severity"
+			case slog.MessageKey:
+				attr.Key = "message"
+			case slog.SourceKey:
+				attr.Key = "source"
+			}
+			return attr
+		},
+	})
+	logger := slog.New(handler).With("service", service)
+	slog.SetDefault(logger)
+	return logger
+}