Add failure handling for export generation errors

Introduce `OnExportGenerationFails` subscriber to handle export generation failures. It logs errors, updates the export status to failure, and records generation errors. Added tests to validate the new functionality.

src/Bundle/ChillMainBundle/Tests/Export/Messenger/OnExportGenerationFailsTest.php

@@ -0,0 +1,62 @@
+<?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\Tests\Export\Messenger;
+
+use Chill\DocStoreBundle\Entity\StoredObject;
+use Chill\MainBundle\Entity\ExportGeneration;
+use Chill\MainBundle\Entity\User;
+use Chill\MainBundle\Export\Exception\ExportGenerationException;
+use Chill\MainBundle\Export\Messenger\ExportRequestGenerationMessage;
+use Chill\MainBundle\Export\Messenger\OnExportGenerationFails;
+use Chill\MainBundle\Repository\ExportGenerationRepository;
+use Doctrine\ORM\EntityManagerInterface;
+use PHPUnit\Framework\TestCase;
+use Prophecy\PhpUnit\ProphecyTrait;
+use Psr\Log\NullLogger;
+use Symfony\Component\Messenger\Envelope;
+use Symfony\Component\Messenger\Event\WorkerMessageFailedEvent;
+
+/**
+ * @internal
+ *
+ * @coversNothing
+ */
+class OnExportGenerationFailsTest extends TestCase
+{
+    use ProphecyTrait;
+
+    public function testOnExportGenerationFails(): void
+    {
+        $exportGeneration = new ExportGeneration('dummy');
+        $exportGeneration->setCreatedAt(new \DateTimeImmutable('10 seconds ago'));
+
+        $repository = $this->prophesize(ExportGenerationRepository::class);
+        $repository->find($exportGeneration->getId())->willReturn($exportGeneration);
+
+        $entityManager = $this->prophesize(EntityManagerInterface::class);
+        $entityManager->flush()->shouldBeCalled();
+
+        $user = $this->prophesize(User::class);
+        $user->getId()->willReturn(1);
+
+        $subscriber = new OnExportGenerationFails(new NullLogger(), $repository->reveal(), $entityManager->reveal());
+
+        $subscriber->onMessageFailed(new WorkerMessageFailedEvent(
+            new Envelope(new ExportRequestGenerationMessage($exportGeneration, $user->reveal())),
+            'dummyReceiver',
+            new ExportGenerationException('dummy_exception'),
+        ));
+
+        self::assertEquals(StoredObject::STATUS_FAILURE, $exportGeneration->getStoredObject()->getStatus());
+        self::assertStringContainsString('dummy_exception', $exportGeneration->getStoredObject()->getGenerationErrors());
+    }
+}