Webfinger

Kitsune uses Webfinger for resolving mentions and such. For example, when mentioning a user in a post in the form @user@instance.org, the mention is interpreted as a Webfinger acct query.
We then connect to the remote server and send an HTTP GET request on the path /.well-known/webfinger with the query parameter resource set to acct:user@instance.org.

The server is then expected to return a Webfinger resource containing a link with the rel property set to self and the href attribute pointing to the ActivityPub actor.

Example Webfinger resource:

{
  "subject": "acct:user@instance.org",
  "aliases": [],
  "links": [
    {
      "rel": "self",
      "href": "https://instance.org/users/user"
    }
  ]
}