Add subject support for Google Workspace Domain-Wide Delegation

[DEEPIKA-217M]

Description

This PR adds support for Google Workspace Domain-Wide Delegation by introducing a subject parameter across the Google provider authentication flow.

Changes made

• Added subject support to GoogleBaseHook.
• Propagated subject through the credentials provider.
• Applied delegated credentials using credentials.with_subject(...) when supported.
• Added subject support to Google Drive, Google Sheets, and Discovery API hooks.
• Updated Google Drive operators and sensors to forward the subject parameter.

Testing

• Verified the code compiles successfully.
• Ran git diff --check with no formatting issues.
• Reviewed the authentication flow to ensure existing impersonation behavior remains unchanged.

Related: #67051

• Yes

Generated-by: chatgpt for some reference

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Important

🛠️ Maintainer triage note for @DEEPIKA-217M · by @potiuk · 2026-07-18 15:46 UTC

Helpful heads-up from the maintainers — please address before this PR can be reviewed:

• ❌ Provider tests. See docs.

See the Pull Request quality criteria for details.

The ball is in your court — you've been assigned to this PR. Fix the above, then mark it Ready for review.

_{Automated triage — may be imperfect; a maintainer takes the next look.}

[boring-cyborg]

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[aaron-y-chen]

Thanks for the contribution! Here is my feedback:

1. Could you add unit tests covering subject, including the case where it is combined with impersonation_chain?
2. Have you tested this against a real Google Workspace / GCP environment? In my experience, credential-related changes, especially Domain-Wide Delegation, are hard to fully verify by relying only on unit tests or mocks.