Redirect small number of users to staging

[jupyterhub]

Redirect small number of users to staging

[yuvipanda]

While I agree this would be a useful thing to have,

1. We must make sure that we don't knowlingly send users to a setup that we know will fail (because automated tests fail, for example)
2. This is useful at high rates of request, where a failure is easily fixable (user just hits refresh). We don't have that volume yet, so we shouldn't do this until we do.
3. We should be very clear on what we are looking to test. For example, with #83, these two would be entirely different clusters, and staging would be much smaller. So it might fail just due to capacity issues, for example.

It's a good idea that we should carefully prioritize and decide what we want to get out of it before we implement. My personal feeling is that we've a while to go before this is useful to us.

[yuvipanda]

I'm going to close this for now, until IMO we're large enough for this kinda deployment to be useful to us. Is that ok with you, @betatim?