Restores passed/grade onto a user’s completions in a course from their active snapshots and then
soft-deletes those snapshots, undoing a cheating confirmation. A no-op for users without active
snapshots (e.g. a student dismissed straight from the flagged state, who was never failed).
Snapshots the current passed/grade of all of a user’s completions in a course and then fails
them (passed = false, grade = 0) as the consequence of a confirmed cheating suspicion. The
snapshots let the failure be undone exactly if the suspicion is later dismissed (see
restore_and_clear_for_user_course). A completion that already has an active snapshot is left
as-is, so confirming an already-confirmed student does not overwrite the original values.