* No need to inform clients of status of remote users; as that will
   arrive in due course anyway. We don't -have- the state currently, so
   we'd only send an unknown message

 * Remember to bump the presence serial for the event source, so the
   notifiers will wake up and report it

Have EventSource's get_new_events_for_user() API work only on keys within that source, not overall eventstream tokens

Avoid hardcoding names of individual stream token keys in its own implementation; this at least reduces the number of places in source code the individual parts are stored

Show desktop notification state. Provide help if the user has previously denied permission to display them.

Only show voice call button if there are exactly 2 members in the room. Also hide the somewhat user unfriendly call state.

Change call signalling messages to be their own types of room events rather than room messages with different msgtypes: room messages should be things that the client can display as a unit message to the user.