This removes user-facing Studio edit support for Old Mongo courses
(courses that have a CourseKey of the format {org}/{course}/{run}).
This does not affect our normal courses, which have CourseKeys
starting with "course-v1:".
After this commit:
* Old Mongo courses will continue to appear on the Studio course
listing page, but are not clickable.
* Any attempt to directly access an Old Mongo course in Studio via URL
fail with a 404 error.
* Course certificates will still be available for Old Mongo courses.
* Old Mongo courses will continue to be returned by CourseOverviews
and get_course_summaries() calls.
We decided against removing Old Mongo courses from the listing entirely
because that would require very expensive CourseOverviews query to
filter them out. Making that query more efficient would involve a
database migration to add appropriate indexing, which is something else
that we are looking to avoid. CourseOverviews are used everywhere in
the system, so we want to avoid changing how they work so that we can
minimize risk.
This is part of the Old Mongo Modulestore deprecation effort:
https://github.com/openedx/public-engineering/issues/62
