Replace the redirect server with a proxy

[tam203]

Currently in order to connect the Hub user to their Azure Compute Instance (CI) they are routed to a service (running in JHub) which sends a redirect header that directs to the AML instance on the JLab url.

This 'breaks out' of the JHub framework and it would be nicer if we could instead proxy to the CI instance as per other JHub setups. However, the CI on Azure has a lot of Auth in front of it and I'm not at all sure that that could be handled by a proxy.

So this issue is to discover:

• Could you theoretically put a proxy in front of AML or does the auth on the AML CI make this impossible.