(BB-1389) Update enrollment serializer and Add problem submission history endpoint
Another description as I don't have permission to edit the above.
This PR adds an endpoint displaying the submission history for each course a specific user is enrolled.
*Sandbox URL*: https://pr20948.sandbox.opencraft.hosting/ (provisioning)
These can use the sandbox above or a devstack.
1. Ensure the logged in user has submitted a few problems.
2. Browse http://localhost:18000/api/enrollment/v1/submission_history or http://pr20948.sandbox.opencraft.hosting/api/enrollment/v1/submission_history
3. Make sure a JSON object showing the user submissions is displayed
Author notes and concerns
1. The update in the enrollment serializer makes extra mongodb calls.
Can you reassign this OSPR to T&L? While the changes are within the enrollments app (owned by website) they logically belong in a courseware app since the changes are related to student history.