Option to require fetches to be signed
Mastodon can (or does?) require object fetches to be signed by an instance actor so it can decide whether to return an object or not. This is supposed to help soft-enforce some blocking schemes, as you can prevent another instances from getting your posts by the usual means.
While we already do sign our fetches, we do not have a similar mechanism to require them for fetches like mastodon does. This should be implemented as a default-off option, as it does not provide very much security.