Add extended reservation checks in the server

[val500]

Description

This PR adds support for extended reservation times in Testflinger Server. Certain users need longer reservation times than the maximum 6 hours, so this provides this ability for authorized clients. The server rejects jobs with higher than 6 hours of requested reservation time if they do not provide credentials or if their credentials do not provide them the authorization. The authentication flow is similar to that of job priority and restricted queues.

Resolved issues

Resolves https://warthogs.atlassian.net/browse/CERTTF-458

Documentation

Documentation was added to the docs/ folder.

Web service API changes

No new endpoints, but jobs that have longer than 6 hours requested of reservation times will be rejected without prior authorization.

Tests

Unit tests were added to test_v1_authorization.py

[plars]

@val500 It looks pretty straightforward so far, but of course needs documentation. Not sure you intended it to be ready for review yet since it's not filled in and marked though.

[boukeas]

I've left quite a lot of comments here and there -- many of them are questions. I am not too familiar with the detail of how all this comes together and I am unaware of any previous discussions you might have had with Paul so I apologize in advance for any of the comments that might be missing the mark.

[boukeas]

I think the structure reflects the logic pretty well now. I have asked for one final refinement but please check that it makes sense and that it works properly. I am approving in any case so that I don't slow you down. Thank you for all this.