UI - Authenticate via SSO beyond timeout period

[nateiam]

As a Shepherd UI user I want to interact with the UI beyond the authentication timeout period so I don't have to reload my browser if a timeout occurs

OSS Note - this is based on assumption that authentication session is only active for 2 hours. After this time, all AJAX will start fail with 403. Some other apps handle this by maintaining a timer in Javascript and as the time approaches -- or prior to any AJAX call after the time is exceeded -- the UI makes another non-ajax call in an invisible IFrame that re-authenticates.

Acceptance Criteria

• Users can interact with the UI after the timeout period with no impact
• Users are transparently re-authenticated immediately before the timeout period or during the next interaction after the timeout period
• This works on both Mac and PC