Add support for following regular users

[kuba-orlik]

@Jagster

I would now like some thoughts and ideas on how on earth we can explain this difference to Mastodon users. I think I understand the basics of why the implementation is like that, but still, we are in a situation where Mastodon users keep trying to follow the wrong actor.

I think the best, ideal solution I would wish for would be to give us a way to follow the regular forum users, as well. Lack of this possibility is really cooling my enthusiasm for federating my Discourse instance, as the confusion of “hey the follows are not working” is scary