logging: Add subsystem to log API (#19002)

Create new code paths for multiple subsystems in the code. This will
make maintaing this easier later.

Also introduce bugLogIf() for errors that should not happen in the first
place.

internal/config/identity/plugin/config.go

@@ -38,6 +38,10 @@ import (
 	xnet "github.com/minio/pkg/v2/net"
 )
 
+func authNLogIf(ctx context.Context, err error) {
+	logger.LogIf(ctx, "authN", err)
+}
+
 // Authentication Plugin config and env variables
 const (
 	URL        = "url"
@@ -434,7 +438,7 @@ func (o *AuthNPlugin) checkConnectivity(ctx context.Context) bool {
 
 	req, err := http.NewRequestWithContext(ctx, http.MethodHead, u.String(), nil)
 	if err != nil {
-		logger.LogIf(ctx, err)
+		authNLogIf(ctx, err)
 		return false
 	}