Cancelling a lesson that was already paid for now credits the student
that money instead of leaving it as a manual refund, and the daily
scheduled-billing scan applies any available credit against their due
charges before emailing the notice.
- New us_credits ledger + us_payments.credit_applied column (Payment::netDue).
- PaymentService::creditForCancelledLesson issues a per-lesson share of the
covering payment's total; wired into all three cancel paths (student
self-cancel, instructor status update, admin student-detail cancel).
- PaymentService::applyCredits draws credit down FIFO across a run's charges,
marking a fully-covered charge paid-by-credit; the notice shows the credit
applied and reduced total, and the admin queue shows net due.
- Student detail page shows a student's credit balance and history.
Ships as part of the unreleased 1.2.0 (same release as scheduled billing).
Tests: composer test (585), composer lint, composer cs all pass.
Co-Authored-By: Claude Opus 4.8 <[email protected]>
