Service account realm roles support

[waldemarschmalz]

This PR adds support to add a realm-role to a service account.

With resource_keycloak_openid_client_service_account_role it was not possible to add realm-roles. Maybe this is not the best solution, but it works.

I added resource_keycloak_openid_client_service_account_realm_role.
Currently it is only possible to add a single role per resource. There are no docs yet.

Maybe resource_keycloak_openid_client_service_account_role and resource_keycloak_openid_client_service_account_realm_role could be merged.

[mrparkers]

Yeah, I agree that these two resources should eventually be merged, but there really isn't a clean way to do that right now. Unfortunately, the way I decided to handle resource IDs when I first started writing this provider makes it difficult to use them them practically. In this case, they could have be used to determine the difference between a realm role and a client role, so another resource wouldn't be needed.

At some point this year I plan to release a 2.0 version that completely reworks how resource IDs are treated which should simplify the code a lot, and allow for this to be condensed into a single resource.

For now I'll merge this for you so you can get the value you need. Thanks for the PR!

[waldemarschmalz]

Thanks!