BatchImportErrorCode classifies per-item batch import failures. - BATCH_IMPORT_ERROR_UNSPECIFIED: No error (import succeeded) - BATCH_IMPORT_ERROR_INVALID_ARGUMENT: The key data is malformed or missing required fields - BATCH_IMPORT_ERROR_ALREADY_EXISTS: A key with this identifier already exists - BATCH_IMPORT_ERROR_FAILED_PRECONDITION: State conflict prevents the import - BATCH_IMPORT_ERROR_INTERNAL: Server error during import