add set scheduling api

backend/app/Schedule/Schedule.php

@@ -0,0 +1,61 @@
+<?php
+
+namespace App\Schedule;
+
+use App\Set\Set;
+use App\User\User;
+use DateTimeImmutable;
+
+final readonly class Schedule
+{
+    /**
+     * @param list<ScheduleAssignment> $assignments
+     */
+    public function __construct(
+        private int $id,
+        private User $user,
+        private Set $set,
+        private string $elementKind,
+        private DateTimeImmutable $startDate,
+        private DateTimeImmutable $targetDate,
+        private array $assignments,
+    ) {}
+
+    public function getId(): int
+    {
+        return $this->id;
+    }
+
+    public function getUser(): User
+    {
+        return $this->user;
+    }
+
+    public function getSet(): Set
+    {
+        return $this->set;
+    }
+
+    public function getElementKind(): string
+    {
+        return $this->elementKind;
+    }
+
+    public function getStartDate(): DateTimeImmutable
+    {
+        return $this->startDate;
+    }
+
+    public function getTargetDate(): DateTimeImmutable
+    {
+        return $this->targetDate;
+    }
+
+    /**
+     * @return list<ScheduleAssignment>
+     */
+    public function getAssignments(): array
+    {
+        return $this->assignments;
+    }
+}