Implement Admin Server

[frankgreco]

It would be nice to have and JSON API that relayed the following relationships:

• Which ApiProxy resources does a specific ApiKey have access to?
• Which ApiKey resources have access to a specific ApiProxy and in what way?

The reason this would need to be another server within the Kanali application as opposed to a separate application is because we want to know the results as Kanali's internal store would interpret them and not what is represented in etcd (although they should be one in the same).

The api specification has not been proposed yet and still needs to be done (openapi please).

This api will start to lay the groundwork for a UI.