limit number of connections on a per connection basis

[timdrysdale]

Problem: For the wave tank, we reckon that classes of say 30 students will want to view the same stream as the teacher. The teacher might have control but the students have a read-only interface. Nonetheless, they will each draw a video stream. We might want to limit that number of connections a class can make, with a single link, so that we can size the relay instance ahead of time, and know that each customer is getting the service they paid for, which might not be the case if a class of 100 log on from one school, e.g. in an assembly,
Solution: consider a way in which to specify max number of connections (probably in the jwt token)