Upgrading a room should rewrite restricted join rules on affected rooms

[Mikaela]

Suggestion

When a room is upgraded, m.room.join_rules in rooms allowing access based on membership of that room should be updated to reflect the new room ID instead of being left for the user to change them manually. Additionally if the room is a Space with m.room.join_rule restricted, it should also allow joining based on membership of the previous version.

This also affects rooms with m.room.join_rule of knock_restricted.

I understand based on element-hq/element-meta#1961 and element-hq/element-web#911 that this must be specced or the client cannot rely on the server having this functionality. I am not sure if this would still belong to the client though, or is it acceptable for the server to act on behalf of the user as long as the user is in affected rooms?