Provide example that shows how to use scopes without any prefix at all

[MarcialRosales]

Is your feature request related to a problem? Please describe.

Some users complain (#2042) that they cannot use scopes without any prefix like tag:administrator or read:*/*. It is not ideal to use scopes without any prefix at all because it is difficult to determine to which resource those scopes refer to.

Describe the solution you'd like

Provide an example using keycloak that shows how to configure an empty scope_prefix. This means adding the example to the docs and one configuration file to the rabbitmq_oauth2_tutorial.

Describe alternatives you've considered

No response

Additional context

No response