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

src/components/sections/MasterClasses.tsx

@@ -279,6 +279,7 @@ export function MasterClasses({ data, regCounts = {} }: MasterClassesProps) {
         endpoint="/api/master-class-register"
         extraBody={{ masterClassTitle: signupTitle }}
         successMessage={data.successMessage}
+        waitingMessage={data.waitingListText}
       />
     </section>
   );