* feat: add course mode expiration explicit to admin
Adds a checkbox for defining the expiration_datetime_is_explicit to the course_mode Django admin screen.
* fix: Change labels to use "lock"
* fix: increment migration name number
* fix: delete migration
delete the migration and recreate in the next commit
* fix: add back migration
Add back the migration to hopefully fix strange failing test.
* fix: fix failing test
831a8bcc36