Fix Update user-related HTTP headers to fix impersonation

[izeigerman]

Description

The latest version of Trino changed how the HTTP headers are handled: https://trino.io/docs/current/develop/client-protocol.html#client-request-headers when the server returns the X-Trino-Set-Authorization-User header.

Thus, the X-Trino-Authorization-User header is no longer supported. Instead, X-Trino-User should be set to the authorization user, and X-Trino-Original-User should be set to the originally authenticated user.

Without these changes, the impersonation doesn't work with the latest versions of trino.

Release notes

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* Fix impersonation support

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[izeigerman]

@hashhar is this something you can help review? Thanks!

The CLA has been signed

[Copilot]

Pull Request Overview

This pull request updates the HTTP header handling to support impersonation with the latest version of Trino. The changes include:

• Adding a new constant (HEADER_ORIGINAL_USER) to represent the original user.
• Updating the client to set HEADER_ORIGINAL_USER and HEADER_USER based on whether an authorization user is provided.
• Adjusting authentication and testing logic to align with the new header mapping.

Reviewed Changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated no comments.

File	Description
trino/constants.py	Added HEADER_ORIGINAL_USER and removed HEADER_AUTHORIZATION_USER.
trino/client.py	Updated header assignment logic to support impersonation.
trino/auth.py	Modified user extraction to prioritize HEADER_ORIGINAL_USER.
tests/unit/test_client.py	Updated tests to reflect the new header behavior.

Comments suppressed due to low confidence (2)

trino/client.py:514

• [nitpick] Consider adding an inline comment explaining that if an authorization user is provided, the request is being impersonated, so the original user is preserved in HEADER_ORIGINAL_USER and the impersonating user is sent via HEADER_USER.

        if self._client_session.authorization_user is not None:

trino/auth.py:556

• [nitpick] Consider adding a comment to clarify that this prioritization ensures that if HEADER_ORIGINAL_USER exists, it is used to accurately represent the originally authenticated user in impersonation scenarios.

        return headers.get(HEADER_ORIGINAL_USER, headers.get(HEADER_USER))