[MCC-1501368] Python Lib - Use Error Handler, Document and Update Messages for Fetch Data ()

[afieraru-mdsol]

feature

• Replace this line with Project title.
• MCC-1501368

Pull request overview
This PR refactors the fetch-data path to use a new DatasetTicket DTO and updates validation errors for fetch_data.

Changes:

• Adds DatasetTicket to transport models.
• Replaces Transport.do_get(ResourceQuery) with Transport.get_ticket(DatasetTicket).
• Updates DefaultDataConnectService.fetch_data to build a DatasetTicket and raise structured validation errors.

[Copilot]

Pull request overview

This PR refactors the fetch-data path to use a new DatasetTicket DTO and updates validation errors for fetch_data.

Changes:

• Adds DatasetTicket to transport models.
• Replaces Transport.do_get(ResourceQuery) with Transport.get_ticket(DatasetTicket).
• Updates DefaultDataConnectService.fetch_data to build a DatasetTicket and raise structured validation errors.

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 8 comments.

File	Description
dataconnect/transport/models.py	Adds the dataset fetch ticket DTO.
dataconnect/transport/base.py	Updates the transport interface for ticket-based fetches.
dataconnect/transport/arrow_flight/transport.py	Serializes DatasetTicket into an Arrow Flight ticket and calls do_get.
dataconnect/service/default.py	Updates fetch_data validation and dispatches through get_ticket.

Comments suppressed due to low confidence (1)

dataconnect/service/default.py:109

• Several of these lines contain trailing whitespace after the comma before the newline, which violates the repository's configured Ruff W rules and will fail linting.

                    timestamp=datetime.now(UTC).strftime("%Y-%m-%dT%H:%M:%SZ"), 
                    details=[ErrorDetail(field="first_n_rows", 
                                        message=f"Received {first_n_rows} for first_n_rows, which is not a positive integer.", 
                                        expected="Set first_n_rows to 1 or greater, or omit the parameter to retrieve the full dataset")],

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