Symfony version(s) affected: 5.x

Description
doctrine-bridge declares some Messenger middlewares (i.e \Symfony\Bridge\Doctrine\Messenger\AbstractDoctrineMiddleware), using ManagerRegistry and Entity Managers.
This feature requires doctrine/orm to work, but doctrine/orm is declared as a dev dependency in doctrine-bridge composer.json file.

How to reproduce

1. Create a Symfony application without doctrine/orm dependency (doctrine/dbal only)
2. Add the messenger component and configure a bus (i.e with rabbit MQ)
3. Declare a messenger middleware on this bus :

framework:
    messenger:
        buses:
            messenger.bus.my_bus:
                middleware:
                    - doctrine_ping_connection

4. Run consumer in prod environment.
5. Dispatch a message in bus

It will output this error : Doctrine ORM Manager named "" does not exist.

Possible Solution
Only use DBAL in messenger middlewares, or declare doctrine/orm as non-dev dependency in composer.json doctrine-bridge file.