feat: React to verified upgrades by unarchiving the course

[kdmccormick]

Replaces the placeholder COURSE_CATALOG_INFO_CHANGED handler with one that ties the events example to the rest of the plugin's archive functionality: when a learner's enrollment goes active in the verified mode, any existing CourseArchiveStatus row marking that course as archived is flipped back to unarchived (and the archive_date cleared, matching views.py).

Modeled as a one-time event reaction rather than a continuous filter rule so that a learner who deliberately re-archives a verified course after the upgrade has that choice respected.

README + apps.py example comment updated to describe the new handler.

Testing

Set up the sample plugin, log in as a user and enroll in a course, go to the learner dashboard, and then archive that course.

From a terminal, run this (update email address, course ID, and tutor dev/local as needed):

tutor dev run lms \
    ./manage.py lms change_enrollment \
    -e 'admin@local.openedx.io' \
    -c 'course-v1:OpenedX+DemoX+DemoCourse' \
    --from audit --to verified

Refresh the learner dashboard. Notice that it's un-archived ✨

Re-architve it, and refresh. Notice that it stays re-archived. Now run this:

tutor dev run lms \
    ./manage.py lms change_enrollment \
    -e 'admin@local.openedx.io' \
    -c 'course-v1:OpenedX+DemoX+DemoCourse' \
    --from verified --to audit

Notice that it stays archived, since we the target mode is audit, not verified.

AI

Claude wrote it all, starting with this prompt:

I want to make the backend-plugin-sample event handler (in signals.py) more interesting and relevant to the rest of the plugin. specifically i'd like this behavior:

• Listen for COURSE_ENROLLMENT_CHANGED
• When caught, if the enrollment change is_active and mode is "verified" (hard-coded string match is OK), then....
  • If the user has archived the course (as saved in CourseArchiveStatus model), then mark it un-archived

the rationale is that if a user has been upgraded to Verified, then the course shouldn't be hidden away in the Archive section of their dashboard (but, if they re-archive it in the future, then we respect that--hence the one-time event handler and not a continuous checking of course mode when computing isArchivedByLearner.

make sense? this might help: https://github.com/openedx/openedx-events. ask questions eagerly

plus some followups about removing COURSE_CATALOG_INFO_CHANGED, updating the docs, and adding tests. I reviewed all the code myself.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 92.99%. Comparing base (913f1b1) to head (5408c81).

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #41      +/-   ##
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+ Coverage   88.40%   92.99%   +4.58%     
==========================================
  Files          14       16       +2     
  Lines         414      471      +57     
  Branches       16       17       +1     
==========================================
+ Hits          366      438      +72     
+ Misses         40       23      -17     
- Partials        8       10       +2     

Flag	Coverage Δ
unittests	92.99% <ø> (+4.58%)	⬆️

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