feat(websocket): add support for reason in WebSocket.close()

[wendy5667]

Summary of Changes

This PR adds reason to Websocket.close() as specified in version 2.3 of the HTTP & WebSocket ASGI Message Format. Closure due to HTTPErrors are rendered automatically from HTTP status code, while others are rendered by a default mapping, which could be changed by users.

Related Issues

Closes #2025

Pull Request Checklist

• [x] Applied changes to both WSGI and ASGI code paths and interfaces (where applicable).
• [x] Added tests for changed code.
• [x] Prefixed code comments with GitHub nick and an appropriate prefix.
• [x] Coding style is consistent with the rest of the framework.
• [x] Updated documentation for changed code.
  • [x] Added docstrings for any new classes, functions, or modules.
  • [x] Updated docstrings for any modifications to existing code.
  • [x] Updated both WSGI and ASGI docs (where applicable).
  • [x] Added references to new classes, functions, or modules to the relevant RST file under docs/.
  • [x] Updated all relevant supporting documentation files under docs/.
  • [x] A copyright notice is included at the top of any new modules (using your own name or the name of your organization).
  • [x] Changed/added classes/methods/functions have appropriate versionadded, versionchanged, or deprecated directives.
• [x] Changes (and possible deprecations) have towncrier news fragments under docs/_newsfragments/, with the file name format {issue_number}.{fragment_type}.rst. (Run towncrier --draft to ensure it renders correctly.)

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 100.00%. Comparing base (206bb38) to head (a53ba4c). Report is 1 commits behind head on master.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #2056 +/- ## ========================================= Coverage 100.00% 100.00% ========================================= Files 63 63 Lines 7178 7218 +40 Branches 1260 1268 +8 ========================================= + Hits 7178 7218 +40 ```

:umbrella: View full report in Codecov by Sentry.
:loudspeaker: Have feedback on the report? Share it here.

[CaselIT]

• I'm not sure if we can always send() a reason indiscriminately inside an ASGI WebSocket protocol message. Maybe it's safer to only include a reason iff we've verified we're dealing with ASGI HTTP+WebSocket protocol spec version 2.3+?

I agree, this seems the safest option

[wendy5667]

• We need to write a newsfragment for the new feature you've implemented.

Could you kindly share the style guide for newsfragments? I couldn't find it in the Contributor's Guide. Thank you!

[CaselIT]

sorry @wendy5667 we kinda forgot this PR. I'll try to bringing it over the finishing line.

[vytas7]

Furthermore, unfortunately it seems that the code got affected by a botched master merge. I can try to fix these things.