[EDUCATOR-3262]

This reverts commit 370501d1.

I rolled back to when we added the oauth2_provider migrations and caused
deployment issues, but they were added to the bok choy cache.

Since we're re-applying those migrations, this should reset bok choy to
a point where it can run our new migrations.

This reverts commit a21b9634.

This reverts commit b8903992.

This reverts commit 80d9bec5.

This reverts commit b9ebe5ea686fc1b16fccd0f276fbc1d53a5c3468.

When searching CourseEnrollments in the admin, list the enrollments
whose usernames were an exact match first.

EDUCATOR-3260

LEARNER-5852

EDUCATOR-2606

another approach

and use the self.assert* convention used by the other tests

when the associated CourseOverview gets recreated.