code: func GetClusterNameSchema(extensionSchema string) string {
  	var clusterNameSchema string
  	if clusterNameSchema == "" {
  		clusterNameSchema = fmt.Sprintf(ClusterNameSpecSchemaTemplate, "")
  	} else {
  		clusterNameSchema = fmt.Sprintf(ClusterNameSpecSchemaTemplate, ","+extensionSchema)
  	}
  	return fmt.Sprintf(V2SchemaTemplate, MetadataSchema, clusterNameSchema, DefaultDefinitions)
  }
docs: // GetClusterNameSchema returns the schema with optionally injected
  // schema for extensions.