feat(redwood): backport instructor APIs conversion to DRF

[Agrendalath]

This backports the conversion of the instruction APIs to REST.

Testing instructions

1. Visit the Instructor dashboard (http://local.edly.io:8000/courses/course-v1:OpenedX+DemoX+DemoCourse/instructor#view-membership) and check that assigning and revoking course roles works correctly.
2. Retrieve the JWT token with curl -X POST -d "grant_type=password&client_id=login-service-client-id&username=<username>&password=<password>&token_type=jwt" http://local.edly.io:8000/oauth2/access_token (replace the username and password with the correct values).
3. Assuming the audit user exists and you have a course course-v1:edX+DemoX+Demo_Course, use the following request to assign a course role: curl -X POST -H "Authorization: JWT <token>" -d "rolename=staff&action=allow&unique_student_identifier=audit" http://local.edly.io:8000/courses/course-v1:OpenedX+DemoX+DemoCourse/instructor/api/modify_access
4. Check that the role is assigned with curl -X POST -H "Authorization: JWT <token>" -d "rolename=staff" http://local.edly.io:8000/courses/course-v1:OpenedX+DemoX+DemoCourse/instructor/api/list_course_role_members
5. Revoke the role with: curl -X POST -H "Authorization: JWT <token>" -d "rolename=staff&action=revoke&unique_student_identifier=audit" http://local.edly.io:8000/courses/course-v1:OpenedX+DemoX+DemoCourse/instructor/api/modify_access
6. Check that the role is no longer assigned with curl -X POST -H "Authorization: JWT <token>" -d "rolename=staff" http://local.edly.io:8000/courses/course-v1:OpenedX+DemoX+DemoCourse/instructor/api/list_course_role_members

Private-ref: BB-9250