test: add 23 unit tests for provider endpoints
Cover all 9 endpoints in providers.py:
- Provider presets (list all, get by ID, not found)
- Gmail credential CRUD (create, update, get, delete)
- Import labels update
- Gmail authorize URL (success, not configured)
- Debug email (success, no credentials, injection failure)
- OAuth callback (new/update cred, not configured, token exchange
failure, missing access token, verification failure)
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
Co-authored-by: christianlouis <361235+christianlouis@users.noreply.github.com>
copilot-swe-agent[bot]
4d1451ecde