Feature: [docgen] generate documents in an async queue

The documents are now generated in a queue, using symfony messenger. This queue should be configured:

```yaml
# app/config/messenger.yaml
framework:
    messenger:
        # reset services after consuming messages
        # reset_on_message: true

        failure_transport: failed

        transports:
            # https://symfony.com/doc/current/messenger.html#transport-configuration
            async: '%env(MESSENGER_TRANSPORT_DSN)%'
            priority:
                dsn: '%env(MESSENGER_TRANSPORT_DSN)%'
            failed: 'doctrine://default?queue_name=failed'

        routing:
            # ... other messages
            'Chill\DocGeneratorBundle\Service\Messenger\RequestGenerationMessage': priority
```

`StoredObject`s now have additionnal properties:

* status (pending, failure, ready (by default) ), which explain if the document is generated;
* a generationTrialCounter, which is incremented on each generation trial, which prevent each generation more than 5 times;

The generator computation is moved from the `DocGenTemplateController` to a `Generator` (implementing `GeneratorInterface`. 

There are new methods to `Context` which allow to normalize/denormalize context data to/from a messenger's `Message`.

src/Bundle/ChillActivityBundle/Service/DocGenerator/ActivityContext.php

@@ -22,6 +22,7 @@ use Chill\DocStoreBundle\Repository\DocumentCategoryRepository;
 use Chill\MainBundle\Templating\TranslatableStringHelperInterface;
 use Chill\PersonBundle\Entity\AccompanyingPeriod;
 use Chill\PersonBundle\Entity\Person;
+use Chill\PersonBundle\Repository\PersonRepository;
 use Chill\PersonBundle\Templating\Entity\PersonRenderInterface;
 use Doctrine\ORM\EntityManagerInterface;
 use Symfony\Bridge\Doctrine\Form\Type\EntityType;
@@ -45,6 +46,8 @@ class ActivityContext implements
 
     private PersonRenderInterface $personRender;
 
+    private PersonRepository $personRepository;
+
     private TranslatableStringHelperInterface $translatableStringHelper;
 
     private TranslatorInterface $translator;
@@ -55,6 +58,7 @@ class ActivityContext implements
         TranslatableStringHelperInterface $translatableStringHelper,
         EntityManagerInterface $em,
         PersonRenderInterface $personRender,
+        PersonRepository $personRepository,
         TranslatorInterface $translator,
         BaseContextData $baseContextData
     ) {
@@ -63,6 +67,7 @@ class ActivityContext implements
         $this->translatableStringHelper = $translatableStringHelper;
         $this->em = $em;
         $this->personRender = $personRender;
+        $this->personRepository = $personRepository;
         $this->translator = $translator;
         $this->baseContextData = $baseContextData;
     }
@@ -206,6 +211,32 @@ class ActivityContext implements
         return $options['mainPerson'] || $options['person1'] || $options['person2'];
     }
 
+    public function contextGenerationDataNormalize(DocGeneratorTemplate $template, $entity, array $data): array
+    {
+        $normalized = [];
+
+        foreach (['mainPerson', 'person1', 'person2'] as $k) {
+            $normalized[$k] = null === $data[$k] ? null : $data[$k]->getId();
+        }
+
+        return $normalized;
+    }
+
+    public function contextGenerationDataDenormalize(DocGeneratorTemplate $template, $entity, array $data): array
+    {
+        $denormalized = [];
+
+        foreach (['mainPerson', 'person1', 'person2'] as $k) {
+            if (null !== ($id = ($data[$k] ?? null))) {
+                $denormalized[$k] = $this->personRepository->find($id);
+            } else {
+                $denormalized[$k] = null;
+            }
+        }
+
+        return $denormalized;
+    }
+
     /**
      * @param Activity $entity
      */