Add RSS feed for Releases

• Please check this box if this contribution uses AI-generated content (including content generated by GitLab Duo features) as outlined in the GitLab DCO & CLA

What does this MR do and why?

Add RSS feed for releases as requested in #30988 (closed)

MR acceptance checklist

Please evaluate this MR against the MR acceptance checklist. It helps you analyze changes to reduce risks in quality, performance, reliability, security, and maintainability.

Screenshots or screen recordings

Screenshots are required for UI changes, and strongly recommended for all other merge requests.

Before	After

Generated XML:

<?xml version="1.0" encoding="UTF-8"?>
<feed xmlns="http://www.w3.org/2005/Atom" xmlns:media="http://search.yahoo.com/mrss/">
<title>Gitlab Shell releases</title>
<link href="http://127.0.0.1:3000/gitlab-org/gitlab-shell/-/releases.atom" rel="self" type="application/atom+xml"/>
<link href="http://127.0.0.1:3000/gitlab-org/gitlab-shell/-/releases" rel="alternate" type="text/html"/>
<id>http://127.0.0.1:3000/gitlab-org/gitlab-shell/-/releases</id>
<updated>2024-04-26T15:27:27Z</updated>
<entry>
  <id>http://127.0.0.1:3000/gitlab-org/gitlab-shell/-/releases/v14.31.0</id>
  <link href="http://127.0.0.1:3000/gitlab-org/gitlab-shell/-/releases/v14.31.0"/>
  <title>test v2</title>
  <summary>Merge branch 'id-release-14-31-0' into 'main'

Release v14.31.0

See merge request https://gitlab.com/gitlab-org/gitlab-shell/-/merge_requests/903

Merged-by: Igor Drozdov &lt;idrozdov@gitlab.com&gt;
</summary>
  <content type="html"></content>
  <updated>2024-04-26T15:27:27Z</updated>
  <published>2024-04-26T15:27:27Z</published>
  <author>
    <name>Administrator</name>
    <email>admin@example.com</email>
  </author>
</entry>
<entry>
  <id>http://127.0.0.1:3000/gitlab-org/gitlab-shell/-/releases/v14.34.0</id>
  <link href="http://127.0.0.1:3000/gitlab-org/gitlab-shell/-/releases/v14.34.0"/>
  <title>test</title>
  <summary>Merge branch 'ashmckenzie/gitlab-shell-release-14-34-0' into 'main'

Release v14.34.0

See merge request https://gitlab.com/gitlab-org/gitlab-shell/-/merge_requests/965

Merged-by: Igor Drozdov &lt;idrozdov@gitlab.com&gt;
Approved-by: Igor Drozdov &lt;idrozdov@gitlab.com&gt;
Approved-by: Alejandro Rodríguez &lt;alejandro@gitlab.com&gt;
Co-authored-by: Ash McKenzie &lt;amckenzie@gitlab.com&gt;</summary>
  <content type="html">&lt;p data-sourcepos="1:1-3:4" dir="auto"&gt;test&amp;#x000A;test&amp;#x000A;test&lt;/p&gt;</content>
  <updated>2024-04-26T15:26:14Z</updated>
  <published>2024-04-25T23:05:51Z</published>
  <author>
    <name>Administrator</name>
    <email>admin@example.com</email>
  </author>
</entry>
</feed>

How to set up and validate locally

Numbered steps to set up and validate the change are strongly suggested.

1. Visit any group or project member pages such as http://127.0.0.1:3000/gitlab-org/gitlab-shell/-/releases
2. Create a release
3. Click the Releases feed button.
4. Inspect generated XML