Support for GET /realms/{realm}/clients/{client-id}/authz/resource-server/settings

[Ullaakut]

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

The API has an endpoint to fetch the authorization config for a resource server. Since resource servers are intended to enforce their rules, being able to fetch their own authorization configuration seems like a useful feature for this library.

In the latest version, this is done by making a GET request against /realms/{realm}/clients/{client-id}/authz/resource-server/settings with an access_token that has view_clients, query_clients and view_authorization as part of its service account roles.

Describe the solution you'd like

Add a method called GetResourceServer which returns a ResourceServerRepresentation (already part of models.go)

Describe alternatives you've considered

Making the HTTP request manually without using gocloak, or using a fork.

Additional context

I already implemented the feature on my fork. I will add unit tests and open a PR.