Add voter for ExportGeneration stored object authorization

Introduces `ExportGenerationStoredObjectVoter` to handle permissions for stored objects linked to export generations. Implements entity association retrieval in `ExportGenerationRepository` by adhering to `AssociatedEntityToStoredObjectInterface`.

src/Bundle/ChillMainBundle/Security/Authorization/StoredObject/ExportGenerationStoredObjectVoter.php

@@ -0,0 +1,41 @@
+<?php
+
+declare(strict_types=1);
+
+/*
+ * Chill is a software for social workers
+ *
+ * For the full copyright and license information, please view
+ * the LICENSE file that was distributed with this source code.
+ */
+
+namespace Chill\MainBundle\Security\Authorization\StoredObject;
+
+use Chill\DocStoreBundle\Entity\StoredObject;
+use Chill\DocStoreBundle\Security\Authorization\StoredObjectRoleEnum;
+use Chill\DocStoreBundle\Security\Authorization\StoredObjectVoterInterface;
+use Chill\MainBundle\Repository\ExportGenerationRepository;
+use Symfony\Component\Security\Core\Authentication\Token\TokenInterface;
+
+final readonly class ExportGenerationStoredObjectVoter implements StoredObjectVoterInterface
+{
+    public function __construct(private ExportGenerationRepository $repository) {}
+
+    public function supports(StoredObjectRoleEnum $attribute, StoredObject $subject): bool
+    {
+        return null !== $this->repository->findAssociatedEntityToStoredObject($subject);
+    }
+
+    public function voteOnAttribute(StoredObjectRoleEnum $attribute, StoredObject $subject, TokenInterface $token): bool
+    {
+        if (StoredObjectRoleEnum::EDIT === $attribute) {
+            return false;
+        }
+
+        if (null === $generation = $this->repository->findAssociatedEntityToStoredObject($subject)) {
+            throw new \UnexpectedValueException('generation not found');
+        }
+
+        return $token->getUser()->getUserIdentifier() === $generation->getCreatedBy()->getUserIdentifier();
+    }
+}