Feature/infrastructure roles (#91)

* Add infrastructure roles configured globally.

Those are the roles defined in the operator itself. The operator's
configuration refers to the secret containing role names, passwords
and membership information. While they are referred to as roles, in
reality those are users.

In addition, improve the regex to filter out invalid users and
make sure user secret names are compatible with DNS name spec.

Add an example manifest for the infrastructure roles.

cmd/main.go

@@ -48,9 +48,9 @@ func ControllerConfig() *controller.Config {
 	restClient, err := k8sutil.KubernetesRestClient(restConfig)
 
 	return &controller.Config{
-		PodNamespace:   podNamespace, //TODO: move to config.Config
-		KubeClient:     client,
-		RestClient:     restClient,
+		PodNamespace: podNamespace, //TODO: move to config.Config
+		KubeClient:   client,
+		RestClient:   restClient,
 	}
 }