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/ChillDocGeneratorBundle/tests/Service/Context/Generator/GeneratorTest.php

@@ -26,13 +26,14 @@ class GeneratorTest extends TestCase
         $template = (new DocGeneratorTemplate())->setFile($templateStoredObject = (new StoredObject())
             ->setType('application/test'));
         $destinationStoredObject = (new StoredObject())->setStatus(StoredObject::STATUS_PENDING);
+        $reflection = new \ReflectionClass($destinationStoredObject);
+        $reflection->getProperty('id')->setAccessible(true);
+        $reflection->getProperty('id')->setValue($destinationStoredObject, 1);
         $entity = new class {};
         $data = [];
 
         $context = $this->prophesize(DocGeneratorContextInterface::class);
         $context->getData($template, $entity, Argument::type('array'))->willReturn($data);
-        $context->storeGenerated($template, $destinationStoredObject, $entity, Argument::type('array'))
-            ->shouldBeCalled();
         $context->getName()->willReturn('dummy_context');
         $context->getEntityClass()->willReturn('DummyClass');
         $context = $context->reveal();
@@ -46,8 +47,11 @@ class GeneratorTest extends TestCase
             ->willReturn('generated');
 
         $entityManager = $this->prophesize(EntityManagerInterface::class);
-        $entityManager->find(Argument::type('string'), Argument::type('int'))
+        $entityManager->find(StoredObject::class, 1)
+            ->willReturn($destinationStoredObject);
+        $entityManager->find('DummyClass', Argument::type('int'))
             ->willReturn($entity);
+        $entityManager->clear()->shouldBeCalled();
         $entityManager->flush()->shouldBeCalled();
 
         $storedObjectManager = $this->prophesize(StoredObjectManagerInterface::class);
@@ -65,8 +69,8 @@ class GeneratorTest extends TestCase
 
         $generator->generateDocFromTemplate(
             $template,
-            'DummyEntity',
             1,
+            [],
             $destinationStoredObject
         );
     }
@@ -89,8 +93,8 @@ class GeneratorTest extends TestCase
 
         $generator->generateDocFromTemplate(
             $template,
-            'DummyEntity',
             1,
+            [],
             $destinationStoredObject
         );
     }
@@ -102,6 +106,9 @@ class GeneratorTest extends TestCase
         $template = (new DocGeneratorTemplate())->setFile($templateStoredObject = (new StoredObject())
             ->setType('application/test'));
         $destinationStoredObject = (new StoredObject())->setStatus(StoredObject::STATUS_PENDING);
+        $reflection = new \ReflectionClass($destinationStoredObject);
+        $reflection->getProperty('id')->setAccessible(true);
+        $reflection->getProperty('id')->setValue($destinationStoredObject, 1);
 
         $context = $this->prophesize(DocGeneratorContextInterface::class);
         $context->getName()->willReturn('dummy_context');
@@ -126,8 +133,8 @@ class GeneratorTest extends TestCase
 
         $generator->generateDocFromTemplate(
             $template,
-            'DummyEntity',
             1,
+            [],
             $destinationStoredObject
         );
     }