Dual-mode API server

[rtannenbaum]

In our maintainers meeting on 10/15 we discussed the possibility of 2 modes for the API server

1. [Current/default] Webserver mode -- includes both job management API (JobStore interface) as well as webserver functionality to handle auth redirect flows.
2. [New] Job management mode -- includes the job management piece only. In this scenario, distributions would manage the auth redirect flow from their frontend.

[lisad]

We think that the webserver functionality and auth redirect flows is already separable from the job management code - operators of DTP servers can already do just the job management piece