testing creates with mentions

[julian]

test post with a mention @eubues_derdarrun@activitypub.academy

[julian]

Here is a reply with a mention @claire@sitedethib.com hopefully it works!

[julian]

@Claire@social.sitedethib.com reply with a mention

[julian]

Here's another reply for @Claire@social.sitedethib.com, but with the replies property sending null instead of [].

cc @devnull@crag.social