closes VICE-4299
flag=discussion_checkpoint
Note: Updating checkpointed dates from the tray
will not work until VICE-4300
Test Plan
1. Create a checkpointed discussion with
various states of override due dates and availability
2. Compare the discussion edit page with the assignTo tray
cards
3. Should display all override due dates corectly
3a. assign to tray locations
discussion show, discussion index, assignment index
Change-Id: Ia7125e027370ee7e96cfd8482e5592961316e59a
Reviewed-on: https://gerrit.instructure.com/c/canvas-lms/+/357825
Reviewed-by: Omar Soto-Fortuño <omar.soto@instructure.com>
Tested-by: Service Cloud Jenkins <svc.cloudjenkins@instructure.com>
Reviewed-by: Juan Chavez <juan.chavez@instructure.com>
QA-Review: Juan Chavez <juan.chavez@instructure.com>
Product-Review: Jason Gillett <jason.gillett@instructure.com>