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`.
