feat(tck): implement createFile JSON-RPC method

[exploreriii]

Problem

Created with guidance of claude - please verify

The TCK driver has a full file-service test specification (6 methods), but the Python TCK server implements none of them, so none of those suites can run against this SDK. The SDK side is already complete under src/hiero_sdk_python/file/ — this is TCK plumbing only.

This issue is the first of six and blocks the other five: it creates tck/param/file.py, tck/response/file.py, and tck/handlers/file.py, which the follow-up methods (getFileContents, getFileInfo, updateFile, deleteFile, appendFile) all build on — and the driver needs createFile to produce a file ID for every other file test.

Solution

Add a createFile handler wrapping FileCreateTransaction, modelled on the existing createTopic handler in tck/handlers/topic.py.

Method contract (from the spec):

Input	Type	Required	Notes
keys	string[]	optional	DER-encoded hex private/public keys; KeyLists are hex of serialized protobuf bytes
contents	string	optional	File contents
expirationTime	string	optional	Seconds since epoch
memo	string	optional	UTF-8, max 100 bytes
commonTransactionParams	object	optional	Already supported via tck/param/common.py

Outputs: fileId (string), status (string, receipt status name).

Implementation steps:

1. Create tck/param/file.py with CreateFileParams(BaseTransactionParams) holding keys: list[str] | None, contents: str | None, expirationTime: int | None, memo: str | None, and a parse_json_params() classmethod. Use the helpers in tck/util/param_utils.py (non_empty_string_list, to_int, parse_session_id, parse_common_transaction_params) — see CreateTopicParams in tck/param/topic.py for the exact pattern, including the isinstance(keys, list) validation before parsing.

2. Create tck/response/file.py with:

   @dataclass
   class CreateFileResponse:
       fileId: str | None = None
       status: str | None = None

3. Create tck/handlers/file.py with the handler:

   @rpc_method("createFile")
   def create_file(params: CreateFileParams) -> CreateFileResponse:
       client = get_client(params.sessionId)
       transaction = FileCreateTransaction().set_grpc_deadline(DEFAULT_GRPC_TIMEOUT)
   
       if params.keys is not None:
           transaction.set_keys([get_key_from_string(k) for k in params.keys])
       if params.contents is not None:
           transaction.set_contents(params.contents)
       if params.expirationTime is not None:
           transaction.set_expiration_time(Timestamp(params.expirationTime, 0))
       if params.memo is not None:
           transaction.set_file_memo(params.memo)
   
       if params.commonTransactionParams is not None:
           params.commonTransactionParams.apply_common_params(transaction, client)
   
       response = transaction.execute(client, wait_for_receipt=False)
       receipt = response.get_receipt(client, validate_status=True)
   
       file_id = ""
       if receipt.status == ResponseCode.SUCCESS and receipt.file_id is not None:
           file_id = str(receipt.file_id)
       return CreateFileResponse(file_id, ResponseCode(receipt.status).name)

4. Register the module — easy to miss: add file to the import tuple in tck/handlers/__init__.py. That import is what triggers the @rpc_method decorators; without it the method silently won't register and the driver gets MethodNotFoundError.

5. Add tests/tck/create_file_handler_test.py following the existing handler-test pattern (mock the client, assert param→setter mapping and response shape).

Details that matter:

• Timestamp(seconds, nanos) takes positional ints — same epoch-seconds pattern as tck/handlers/account.py (Timestamp(params.expirationTime, 0)).
• get_key_from_string() (tck/util/key_utils.py) handles both private and public DER hex per element.
• Only call a setter when the param is not None — omitted vs. explicitly-set are distinct test cases in the spec.

Acceptance criteria

• createFile registered and dispatchable (get_all_handlers() contains it)
• All inputs mapped; omitted params leave SDK defaults untouched
• Returns fileId + status; fileId is empty string on non-SUCCESS
• file module added to tck/handlers/__init__.py
• Unit test added; uv run pytest tests/tck -q passes

Spec: https://github.com/hiero-ledger/hiero-sdk-tck/blob/main/docs/test-specifications/file-service/FileCreateTransaction.md

JS reference: https://github.com/hiero-ledger/hiero-sdk-js/blob/main/tck/methods/file.ts (createFile)

[github-actions]

Thanks for your submission.

This issue is awaiting approval from @hiero-ledger/hiero-sdk-python-triage and @hiero-ledger/hiero-sdk-python-committers and @hiero-ledger/hiero-sdk-python-maintainers.