Fix mutlipe bugs when integrating with Open edX

[OmarIthawi]

Overview

I installed the course access groups app into devstack with the steps below and found a couple of bugs. I fixed those bugs and tested the CAG app and saw it working properly after the fix.

Steps to Install CAG

Set FEATURES["ORGANIZATIONS_APP"] = true in both lms.env.json and cms.env.json.
Set "ENABLE_COURSE_ACCESS_GROUPS": true in Site Configuration.

$ cd ~/work/tahoe-hawthorn/src/
$ git clone git@github.com:appsembler/course-access-groups.git cag
$ cd ../devstack
$ make COMMAND='pip install -e /edx/src/cag -e /edx/src/search' tahoe.exec.edxapp
$ make lms-restart studio-restart
$ python manage.py lms --settings=devstack_docker migrate

You should be able to control the CAG model from within: http://localhost:18000/admin/course_access_groups/

Good luck fiddling with it.

List of Bug Fixes

• bug fix: MembershipRule queries was not working:

  After account activation, the automatic Membership objects were not created.

• bug fix: cag admin cannot add GroupCourse:

  Because Django admin by default cannot deal with CourseKey.

• fix bug: edx-organizaitons app is a requirement for CAG:

  Disabling ORGANIZATIONS_APP in either lms.env.json or cms.env.json makes CAG goes awry.

• Refactor acl_backends.user_has_access to use AccessResponse:

  My bad. I assumed that has_access returns native True/False but it turns out it returns an AccessResponse() object.

• fix query bug: don't check Membership for AnonymousUser:

  Otherwise 500 errors would happen when using the CAG feature with AnonymousUser.

• Simplify check for public courses for AnonymousUser:

  Otherwise 500 errors would happen when using the CAG feature with AnonymousUser.

• Fix exception when platform passes CourseDescriptorWithMixins to user_has_access:

  So it works with both course like objects: CourseOverview (mysql) and CourseDescriptorWithMixins (mongo).

Related PRs

Also see the related platform PR: appsembler/edx-platform#543