add dated assignment endpoint

backend/app/Schedule/ScheduleRepository.php

@@ -3,6 +3,7 @@
 namespace App\Schedule;
 
 use App\User\User;
+use DateTimeImmutable;
 
 interface ScheduleRepository
 {
@@ -14,4 +15,12 @@ interface ScheduleRepository
      * @return list<Schedule>
      */
     public function findAllForUser(User $user): array;
+
+    /**
+     * @return list<AssignmentForDate>
+     */
+    public function findAssignmentsForUserOnDate(
+        User $user,
+        DateTimeImmutable $date,
+    ): array;
 }