Instructors can now see their own group classes under My Lessons →
My Group Classes (view_own_lessons): each class shows its active
enrolment count against capacity plus a roster of enrolled students
with enrolment and payment status.
GroupClassController gains renderInstructorPage(), backed by the
existing per-instructor enrolment query and a newly injected
PaymentRepository for payment status. Wired as a submenu under the
existing My Lessons menu, inside the same !view_all_lessons guard so
owner-operators don't get a duplicate item.
Closes#71
Co-Authored-By: Claude Opus 4.8 <[email protected]>
