Upload callback, used to notify which file resources need to be copied after uploading files. To prevent API timeouts, a single request is limited to a maximum of 100 files. You can split larger batches into multiple requests using the same resource_uuid. However, repeatedly uploading the same file will consume additional resources, and concurrent uploading is strongly discouraged.Note etag is a hash value assigned to a file by the storage bucket, used to verify file integrity Get example (Go code)