Better support remote authorization in the API

[ResidentMario]

The use case here is having a remote machine which is using Quilt to perform some work that it needs to be authorized for. The current login flow doesn't work very well for this use case.

Right now you have to use a workaround: #770.

We could provide an environment variable that allows users to reference the authorization file remotely. That would greatly improve usability for this use case. Note that this is just one suggested solution, and it makes sense to me, but maybe on further reflection something different would work better.

[bussiere]

+1