Remove all the "double return" statements which were a result of us removing all the instances of
```
defer.returnValue(...)
return
```
statements when we switched to python3 fully.
Closes#4583
Does slightly less than #5045, which prevented a room from being upgraded multiple times, one after another. This PR still allows that, but just prevents two from happening at the same time.
Mostly just to mitigate the fact that servers are slow and it can take a moment for the room upgrade to actually complete. We don't want people sending another request to upgrade the room when really they just thought the first didn't go through.
Replaces DEFAULT_ROOM_VERSION constant with a method that first checks the config, then returns a hardcoded value if the option is not present.
That hardcoded value is now located in the server.py config file.
Allow for the creation of a support user.
A support user can access the server, join rooms, interact with other users, but does not appear in the user directory nor does it contribute to monthly active user limits.
Fixes handling of rooms where we have permission to send the tombstone, but not
other state. We need to (a) fail more gracefully when we can't send the PLs in
the old room, and (b) not set the PLs in the new room until we are done with
the other stuff.
Currently when fetching state groups from the data store we make two
hits two the database: once for members and once for non-members (unless
request is filtered to one or the other). This adds needless load to the
datbase, so this PR refactors the lookup to make only a single database
hit.
This is the first tranche of support for room versioning. It includes:
* setting the default room version in the config file
* new room_version param on the createRoom API
* storing the version of newly-created rooms in the m.room.create event
* fishing the version of existing rooms out of the m.room.create event
