83163e58f8
The code changes needed to get CohortMembership functioning properly. The key of this change is twofold: first, CohortMemberships are unique per-user, per-course. This is enforced at the database level. Secondly, the updates are done using a select_for_update, which ensures atomicity.
Open edX -------- This is the root package for Open edX. The intent is that all importable code from Open edX will eventually live here, including the code in the lms, cms, and common directories. Note: for now the code is not structured like this, and hence legacy code will continue to live in a number of different packages. All new code should be created in this package, and the legacy code will be moved here gradually.