feat(HTTP): Refresh 5XX response pages

[bsmth]

Description

This PR refreshes the 5XX HTTP status response code pages.

Motivation

Keeping content up-to-date and useful.

additions:

• Examples in HTTP format
• See also links to HTTP status codes page
• Unify formatting with current conventions (e.g., ## Example to ## Examples with subsections)

Related issues and pull requests:

• [x] https://github.com/mdn/content/pull/35023
• [x] https://github.com/mdn/content/pull/34422
• [ ] https://github.com/mdn/content/pull/35353
• [x] https://github.com/mdn/content/pull/34620

[github-actions[bot]]

Preview URLs (11 pages)

• /en-US/docs/Web/HTTP/Status/500
• /en-US/docs/Web/HTTP/Status/501
• /en-US/docs/Web/HTTP/Status/502
• /en-US/docs/Web/HTTP/Status/503
• /en-US/docs/Web/HTTP/Status/504
• /en-US/docs/Web/HTTP/Status/505
• /en-US/docs/Web/HTTP/Status/506
• /en-US/docs/Web/HTTP/Status/507
• /en-US/docs/Web/HTTP/Status/508
• /en-US/docs/Web/HTTP/Status/510
• /en-US/docs/Web/HTTP/Status/511

External URLs (4)

URL: /en-US/docs/Web/HTTP/Status/501 Title: 501 Not Implemented

• https://learn.microsoft.com/en-us/aspnet/web-api/overview/testing-and-debugging/troubleshooting-http-405-errors-after-publishing-web-api-applications (1 time) (Note! This may be a new URL 👀)

---

URL: /en-US/docs/Web/HTTP/Status/506 Title: 506 Variant Also Negotiates

• https://github.com/apache/httpd/blob/6a2433cb3fbc30c8a55f450a046e4b0f69e73143/modules/mappers/mod_negotiation.c (1 time) (Note! This may be a new URL 👀)
• https://httpd.apache.org/docs/2.4/content-negotiation.html (1 time) (Note! This may be a new URL 👀)
• https://httpd.apache.org/docs/trunk/mod/mod_negotiation.html (1 time) (Note! This may be a new URL 👀)

(comment last updated: 2024-08-30 09:01:03)

[hamishwillee]

A bunch of mostly nits.

[hamishwillee]

@bsmth Just nits now. Approved so you can self-merge after looking at them.

[bsmth]

@bsmth Just nits now. Approved so you can self-merge after looking at them.

Thanks a lot, applied your suggestions and added some more details about server "maintenance mode" cases for 503s.