add X-RH-Identity authentication checks

[martinpitt]

look at the X-RH-Identity header from both the browser (user type) and the target machine (system type), check that the org IDs match. Mention the org ID in the /status reply.

This requires changing the bridge connector to connect with a TLS certificate instead of basic auth.

We need to do some mocking to be able to do that with podman and in the tests. We can just generate another cert pair for the connected host, and add the header in our 3scale container.

[martinpitt]

I sent PR #64 to provide the basic building blocks for this. But it's only a prerequisite, not fixing this issue yet.