Add support for RabbitMQ secret engine

[ThiagoFelippi]

I'm using the vault-secrets-operator with kv secretEngine, but now I'm migrating the RabbitMQ to use credentials from RabbitMQ secret engine at Vault. So I like to suggest the implementation of RabbitMQ secretEngine.

To get the credentials with CLI: vault read rabbitmq/creds/my-role
An idea of CRD manifest, could be:

  apiVersion: ricoberger.de/v1alpha1
  kind: VaultSecret
  metadata:
    name: test-rabbit
  spec:
    secretEngine: rabbitmq
    role: my-vhost
    path: rabbitmq
    type: Opaque

[ricoberger]

Hi @ThiagoFelippi thanks for your suggestions, this sounds like a good idea.

I'm currently a bit short on time, but if you want to contribute this feature a PR would be very welcome.