edx-platform fix: allow only enrolled users in course forum related roles

Description

The course team management section under Instructor > Membership tab allows users to be added a role even if are not enrolled in the course. This is not the expected behaviour based on the help text displayed in the section.

This PR updates update_forum_role_membership api to check whether user is enrolled before adding them to a role.

Supporting information

Private-ref: BB-7543

Testing instructions

Setup master devstack or tutor locally.
Register two users, one of which should have staff access.
Using the staff user, enroll to a course.
Under Instructor > Membership tab, go to Course Team Management section.
Without the changes in this PR, you will be able to add the other user (who did not enroll in this course) to any role.
With the changes in this PR, it will raise an error with appropriate msg.

Other information

A point of discussion: Should we revoke user's course related roles when they unroll from a course?

Jun 13 '23 10:06 navinkarkera

Thanks for the pull request, @navinkarkera! Please note that it may take us up to several weeks or months to complete a review and merge your PR.

Feel free to add as much of the following information to the ticket as you can:

supporting documentation
Open edX discussion forum threads
timeline information ("this must be merged by XX date", and why that is)
partner information ("this is a course on edx.org")
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Jun 13 '23 10:06 openedx-webhooks

@kaustavb12 As per your suggestion, I am splitting up changes related to course team roles (Admin/staff roles) into a separate PR due to inconsistency in studio and lms interfaces. Now this PR holds only forum roles related change, i.e., only enrolled users can be added to forum roles via instructor dashboard.

Jun 23 '23 13:06 navinkarkera

Hi @openedx/teaching-and-learning! Would someone be able to review / merge this for us? Thanks!

Jul 25 '23 20:07 mphilbrick211

Hi @navinkarkera! Flagging the new tests per the recent update: https://discuss.openedx.org/t/minor-change-to-edx-platform-check-statuses/11131

Sep 12 '23 18:09 mphilbrick211

Hi @openedx/teaching-and-learning! Friendly ping on this.

Sep 14 '23 14:09 mphilbrick211

Hi @navinkarkera and @gabor-boros! Just flagging that a failing check has popped up.

Oct 03 '23 01:10 mphilbrick211