Add keycloak admin client

[stuartwdouglas]

Fixes #6350

[sberyozkin]

Hi Stuart @stuartwdouglas, nice and simple, thanks.
I'd only consider move the tests to integration-tests/oidc as integration-tests/oidc-code-flow, as a lot is already going on the other oidc-code-flow tests :-).
Pedro, @pedroigor, what do you think about updating KeycloakRealmResourceManager ? This now also works over HTTPS. I suppose updating a single KeycloakRealmResourceManager would do.

[sberyozkin]

@gsmet Hi, I've removed a backport label for now as I'm not 100% sure it is a new feature or a bug fix :-)

[pedroigor]

Always a learning experience to see @stuartwdouglas code and how to do simple things that work in Quarkus.

[sberyozkin]

@pedroigor I'm replacing this code now, pretty simple with the admin client :-)

[pedroigor]

@sberyozkin Yeah, it should make things lot simpler when interacting to Keycloak REST API.

[sberyozkin]

@pedroigor I'm having issues in replacing the code across all the tests (this is only related to the use of the API, Stuart's PR is fine), so I will just update oidc-code-flow resource and it should be ready to go

[sberyozkin]

Hi @pedroigor So I've updated oidc-code-flow and keycloak-authorization.
oidc did not work as it now uses HTTPS and there is only a single factory method in the api which allows to disable the trust manager, I thought it worked but then in the end it did not. I also could not update oidc-multitenancy. I'm not worried at all, it is really about the correct use of the API, so may be you can have a look later on or may be we can keep some RestAssured code there too.
IMHO it is now ready to go :-)

[gsmet]

@stuartwdouglas I wonder if we should index the jar instead so that things are properly registered for reflection? Otherwise, there's a good chance things won't work very well in native.