Support time based access to groups of cases

[masonlr]

Goal

Support time based access to groups of cases. We want restrict access of users/teams/etc to specific sets of cases. This feature allows us to support tiered subscriptions.

Acceptance criteria

• [ ] Middleware (or user management app) supports concept of case groups
• [ ] End date can be specified for users/teams
• [ ] Test with mock access end date

Out of scope

Implementation notes

• Accounting to be runnable separate from middleware. Current accounting implementation is https://github.com/alan-turing-institute/science-gateway-counter