Auth: Introduce authn.SSOClientConfig to get client config from SSOSettings service (#94618)

* wip

* possible solution

* Separate interface for SSO settings clients

* Rename interface

* Fix tests

* Rename

* Change GetClientConfig to comma ok idiom

pkg/services/authn/authnimpl/service.go

@@ -380,6 +380,20 @@ func (s *Service) IsClientEnabled(name string) bool {
 	return client.IsEnabled()
 }
 
+func (s *Service) GetClientConfig(name string) (authn.SSOClientConfig, bool) {
+	client, ok := s.clients[name]
+	if !ok {
+		return nil, false
+	}
+
+	ssoSettingsAwareClient, ok := client.(authn.SSOSettingsAwareClient)
+	if !ok {
+		return nil, false
+	}
+
+	return ssoSettingsAwareClient.GetConfig(), true
+}
+
 func (s *Service) SyncIdentity(ctx context.Context, identity *authn.Identity) error {
 	ctx, span := s.tracer.Start(ctx, "authn.SyncIdentity")
 	defer span.End()