Feat: Avoid adding of existing availabilities

src/Entity/Availability.php

@@ -10,9 +10,15 @@ use Doctrine\Common\Collections\ArrayCollection;
 use Doctrine\Common\Collections\Collection;
 use Doctrine\DBAL\Types\Types;
 use Doctrine\ORM\Mapping as ORM;
+use Symfony\Bridge\Doctrine\Validator\Constraints\UniqueEntity;
 use Symfony\Component\Validator\Constraints as Assert;
 
 #[ORM\Entity(repositoryClass: AvailabilityRepository::class)]
+#[UniqueEntity(
+    fields: ['dateFrom', 'dateTo'],
+    message: 'Eine Verfügbarkeit für diesen Zeitraum ist bereits vorhanden',
+    repositoryMethod: 'assertUnique'
+)]
 class Availability implements BlameableEntityInterface, TimestampableEntityInterface, SoftDeletableEntityInterface
 {
     use BlameableEntity;