Ability to force clear cache of student enrollment count

[brianhogg]

Is your feature request related to a problem? Please describe.
The course enrollment count under LifterLMS > Reporting > Courses, and selecting a course might not be accurate. It's cached via the enrolled_students meta on the course, and updated using the class.llms.processor.course.data.php background processor.

Describe the solution you'd like
Ability to clear the cache for a single course, or perhaps all courses.

Describe alternatives you've considered
This may just be investigating and documenting how often the enrolled student count is updated, and when it is cleared. There may also be a situation where filters like llms_student_query_get_students are being used to filter out certain students, which impacts the final count of the background processor (we can document this).

[brianhogg]

This should be calculated correctly now via the background processor, which was not saving before and would stop running due to the 9.2.0 update. An extra cache clear could still be useful.