feat: admin-editable success + waiting list messages for MC and Open Day

src/components/sections/OpenDay.tsx

@@ -132,6 +132,8 @@ export function OpenDay({ data }: OpenDayProps) {
           subtitle={signup.label}
           endpoint="/api/open-day-register"
           extraBody={{ classId: signup.classId, eventId: event.id }}
+          successMessage={event.successMessage}
+          waitingMessage={event.waitingListText}
         />
       )}
     </section>