**Symfony version(s) affected**: 4.1 **Description** `routing_key` parameter is always `null` [here](https://github.com/symfony/symfony/blob/master/src/Symfony/Component/Messenger/Transport/AmqpExt/Connection.php#L101) **Additional context** I want to use `messenger` to send messages to a third party application, so I cant modify the way the messages will be consumed