fURL manager can accept and reject fURL requests

Story: https://www.agileplannerapp.com/boards/105200/cards/5090

Here, fURL managers can accept / reject fURL requests.  On accepting the request, a redirect item is pushed into the publishing API (aka. content API) to set up a real redirect.

Contrary to a previous assumption, Alex T informs me that each publishing app should be the canonical source of the material it is publishing, so we are persisting redirects locally also.