Change default rabbitmq vhost to be compatible with DSN parsing in Mautic

[mollux]

the default RabbitMQ vhost is named /, which is encoded to %2F

See https://www.cloudamqp.com/blog/what-is-a-rabbitmq-vhost.html#:~:text=When%20configuring%20RabbitMQ%2C%20at%20least,to%20create%20a%20new%20vhost. and https://symfony.com/doc/current/messenger.html#amqp-transport

There is a bug in Mautic 5 (still figuring out what's going on), that prevents storing the %2F value when saving the settings via the UI.

This PR provides a workaround, by renaming the default RabbitMQ vhost from / to mautic

To test this PR:

• go to the rabbitmq-worker example dir

  ❯ cd examples/rabbitmq-worker

• start the example

  ❯ docker compose up -d

• install Mautic via the UI or CLI UI go to http://localhost:8003

  CLI

  
  docker compose exec -u www-data -w /var/www/html mautic_web php ./bin/console mautic:install http://localhost:8003 -f --admin_email=admin@example.com --admin_password=mautic

• verify the output of the worker container and check if the queue processing started

  ❯  docker compose logs mautic_worker --no-log-prefix -n100 | grep "[OK] Consuming messages from"
  ...
  [OK] Consuming messages from transport "failed".
  [OK] Consuming messages from transport "email".
  [OK] Consuming messages from transport "hit".
  [OK] Consuming messages from transport "hit".
  [OK] Consuming messages from transport "failed".
  [OK] Consuming messages from transport "email".
  
  ...

[renanwilliam]

I'm getting an error vhost mautic/messages not found when trying to send any e-mail using queue:

[renanwilliam]

Looks like is necessary remove the /messages from DSN configuration

[mautibot]

This pull request has been mentioned on Mautic Forums. There might be relevant details there:

https://forum.mautic.org/t/delayed-actions-are-not-being-executed/31995/9