Copied from what I wrote on #19133 discussion: Handling username case is a very tricky issue and I've already encountered a Mastodon <-> Gitea federation bug due to Gitea considering Ta180m and ta180m to be the same user while Mastodon thinks they are two different users. I think the best way forward is for Gitea to only use the original case version of the username for federation so other AP software don't get confused.
This adds the [Webfinger](https://webfinger.net/) endpoint for federation.
Supported schemes are `acct` and `mailto`. The profile and avatar url are returned as metadata.