add assignment completion api

backend/app/Schedule/ScheduleAssignment.php

@@ -4,7 +4,7 @@ namespace App\Schedule;
 
 use DateTimeImmutable;
 
-final readonly class ScheduleAssignment
+final class ScheduleAssignment
 {
     /**
      * @param list<string> $path
@@ -16,6 +16,7 @@ final readonly class ScheduleAssignment
         private array $path,
         private DateTimeImmutable $scheduledDate,
         private int $position,
+        private ?DateTimeImmutable $completedAt,
     ) {}
 
     public function getId(): int
@@ -50,4 +51,21 @@ final readonly class ScheduleAssignment
     {
         return $this->position;
     }
+
+    public function getCompletedAt(): ?DateTimeImmutable
+    {
+        return $this->completedAt;
+    }
+
+    public function complete(DateTimeImmutable $completedAt): void
+    {
+        if ($this->completedAt === null) {
+            $this->completedAt = $completedAt;
+        }
+    }
+
+    public function reopen(): void
+    {
+        $this->completedAt = null;
+    }
 }