docs: document undocumented env vars in configuration overview

[nuthalapativarun]

Problem / Summary

Several environment variables present in .env are not documented in docs/source/configuration/overview.md, making self-hosting harder: USE_USER_TOKEN, AUTOMATIC_LOGIN, COUPLE_SESSION_WITH_COOKIE_NAME, and PUBLIC_FEATURE_ANNOUNCEMENTS.

Solution / Changes

• Add a Feature Announcements subsection under ## Feature Flags documenting PUBLIC_FEATURE_ANNOUNCEMENTS, including the JSON5 array format and maxDate semantics.
• Add three subsections under ## User Authentication documenting:
  • AUTOMATIC_LOGIN — forces OAuth redirect on every unauthenticated request
  • USE_USER_TOKEN — forwards the logged-in user's OAuth token to the inference endpoint instead of OPENAI_API_KEY
  • COUPLE_SESSION_WITH_COOKIE_NAME — ties Chat UI sessions to an external auth cookie so sessions are invalidated on external auth changes
• Auto-formatted overview.md with Prettier (the file was already failing the formatter check before this PR).
• Excludes REASONING_SUMMARY and TEXT_MIME_ALLOWLIST, which are covered by open PRs docs: document REASONING_SUMMARY env flag #2290 and feat: make TEXT_MIME_ALLOWLIST extendable via env var #2353 respectively.

[nuthalapativarun]

Following up on this docs PR — no activity yet after a week. Let me know if the documentation format/structure needs any tweaks, happy to iterate.

[gary149]

Thanks for taking the time to open this. We're closing it as part of a batch of unsolicited, AI-generated PRs that were opened across many repositories at once, which we don't have the bandwidth to review and vet individually.

If there's a specific issue you'd like to work on, please comment on that issue first so we can coordinate scope before any PR is opened. We're happy to engage with focused, individually-motivated contributions. Closing for now, no hard feelings.