fractal-matrix-api: set history visibility for direct chats

We didn't specify the visibility for participants in direct chats. The default behavior when unspecified is confusing,
and leads to messages sent between the sending of an invite
and the acceptance of it being dropped.

Now we append a state event to our room creation that
sets the room visibility to "invited", meaning users
can see messages from when they were invited.

Closes GNOME/fractal#327
4 jobs for <span class="ref-name">wip/christopherdavis/change-direct-chat-visibility</span> in 36 minutes and 22 seconds
Status Job ID Name Coverage
  Check
passed #243892
check

00:01:20

 
  Test
passed #243893
flatpak

00:32:58

 
  Review
passed #243894
review

00:02:04

manual #243895
allowed to fail manual
stop_review