* Add query API for listing active invites
This lists the invites for a user in a room that could be used to
join the room over federation.
* s/Lookup/Look up/
* Fix implements comments
* Add database functions to interact with aliases
* Save room alias
* Check if alias already exists
* Implement local alias lookup
* Implement alias removal
* Move alias API
* Handle case with no alias set for a room
* Apply requested changes