Document Client ID Metadata Document support in the auth API

[kingpanther13]

Proposed change

Documents the Client ID Metadata Document (draft-ietf-oauth-client-id-metadata-document) fallback for redirect URL discovery added in home-assistant/core#176286. The auth API page currently only documents same-host redirect URLs and HTML link tags; this adds the JSON metadata document option with its validation requirements (https client ID, direct 200 response, client_id round-trip, absolute redirect URIs, exact matching).

Type of change

• Document existing features within Home Assistant
• Document new or changing features for which there is an existing pull request elsewhere
• Spelling or grammatical corrections, or rewording for improved clarity
• Editing or restructuring documentation guidelines
• Changes to the backend of this documentation
• Remove stale or deprecated documentation

Checklist

• I have read and followed the documentation guidelines.
• I have verified that my changes render correctly in the documentation.

Additional information

• This PR fixes or closes issue: fixes #
• Link to relevant existing code or pull request: Support Client ID Metadata Documents when verifying redirect_uri core#176286

Summary by CodeRabbit

• Documentation
  • Added guidance for declaring approved OAuth redirect URIs through a Client ID Metadata Document.
  • Documented validation requirements, including HTTPS access, direct successful responses, matching client IDs, absolute URIs, exact comparisons, and the 10 kB scan limit.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro

Run ID: 993170b7-b64d-4971-9440-208d9d2c1836

📥 Commits

Reviewing files that changed from the base of the PR and between f337539 and 0736df5.

📒 Files selected for processing (1)

• docs/auth_api.md

---

📝 Walkthrough

Walkthrough

Documents an alternative OAuth redirect URI declaration using a Client ID Metadata Document, including its JSON format, HTTPS and response requirements, client ID matching, absolute URI validation, exact comparisons, and 10kB scan limit.

Changes

OAuth redirect URI metadata

Layer / File(s)	Summary
OAuth Client ID Metadata Document docs/auth_api.md	Documents the JSON format and validation requirements for serving approved OAuth redirect URIs from the client ID URL.

Estimated code review effort: 1 (Trivial) | ~2 minutes

Possibly related issues

• home-assistant/core#176282 — Documents the CIMD JSON-fetch behavior described as missing from fetch_redirect_uris().

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly matches the main change: documenting Client ID Metadata Document support in the auth API.
Description check	✅ Passed	The description follows the template and fills the required sections with a clear summary, change type, checklist, and related PR link.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

---

Thanks for using CodeRabbit! It's free for OSS, and your support helps us grow. If you like it, consider giving us a shout-out.

❤️ Share

• X
• Mastodon
• Reddit
• LinkedIn

_{Comment @coderabbitai help to get the list of available commands.}