ImportTransferProgressRequest(ImportTransferProgressRequest)

file-transfer.v2 progress callback from the worker.
Matches CallbackMixin._build_progress_payload().

{
    "file_id": "string",
    "progress": 0,
    "speed": 0,
    "upload_id": "string",
    "contract_version": "string",
    "app_key": "string",
    "idempotency_key": "string",
    "meta_data": {
        "property1": "string",
        "property2": "string"
    },
    "transferred_bytes": 0,
    "total_bytes": 0,
    "occurred_at": "string"
}