Better logging in BaseClient
Another change to logging in BaseClient
Explicitly handle Unauthorized responses in ResourceClient
Support 409 Unauthorized in ResourceClient.create
Ensure that Authenticator does not swallow failures

If any of the Futures fail in CompositeAuthenticator, blow up. It is a big deal
if either a) an API cannot reach useless-core, or b) useless-core cannot
reach it's Mongo instance.
Failed attempt at a thread-safe Mockable

It probably has something to do with the ExecutionContexts, but multiple
of the same mock cannot happen in the same test run. Either way, the new
implementation of Mockable is better than the previous.
Insert JsonClient between BaseClient and ResourceClient