RSS feeds use relative links (missing instance address)

[Mikaela]

Description

The Gitea RSS links are relative, so they seem to be nonfunctional outside of web browsers assuming the links are meant to be clicked.

Example item from try.gitea.io:

    <item>
      <title>Mikaela pushed to &lt;a href=&#34;/Mikaela/gist-manual/src/branch/master&#34;&gt;master&lt;/a&gt; at &lt;a href=&#34;/Mikaela/gist-manual&#34;&gt;Mikaela/gist-manual&lt;/a&gt;</title>
      <link>/Mikaela/gist-manual/commit/b4c727723b718991367137c71e58d73a3869b25e</link>
      <description>&lt;a href=&#34;/Mikaela/gist-manual/commit/b4c727723b718991367137c71e58d73a3869b25e&#34;&gt;b4c727723b718991367137c71e58d73a3869b25e&lt;/a&gt;&#xA;matrix/m.room.join_rules: add FluffyChat to knock_restricted</description>
      <content:encoded><![CDATA[<a href="/Mikaela/gist-manual/commit/b4c727723b718991367137c71e58d73a3869b25e">b4c727723b718991367137c71e58d73a3869b25e</a>
matrix/m.room.join_rules: add FluffyChat to knock_restricted]]></content:encoded>
      <author>Mikaela</author>
      <guid>391174</guid>
      <pubDate>Sun, 07 Aug 2022 22:25:56 +0000</pubDate>
    </item>

I got this from curl -LO https://try.gitea.io/Mikaela.rss and the issue has been observed using Limnoria IRC bot and Maubot RSS plugin on Matrix.

Gitea Version

1.17.1

Can you reproduce the bug on the Gitea demo site?

Yes

Log Gist

N/A

Screenshots

N/A

Git Version

N/A

Operating System

N/A

How are you running Gitea?

N/A

Database

No response