Limit number of bridgeable rooms in the config.

[Half-Shot]

As a administrator, I want to set some hard limits on the number of rooms bridged via my instance. Basically this would take the form of a key max_bridged_rooms and would track the number via the database. If the limit is reached, a customizable error should be displayed to the user.

I'm happy to work on this feature

[Half-Shot]

This comes with the added faff of potentially breaking puppeting mode, where you join private rooms by syncing your account. Hmm :/