Implement group resource (#181)

This change implements a new group resource. 

It also sets the standard for a resource reference will be done through
out the controller. A resource reference can either be done by ID or as
a local named reference to the actual resource. This allows end users to
chose if they want to manage things completely in the cluster or not.

Part of #172

Signed-off-by: Philip Laine <philip.laine@gmail.com>

PROJECT

@@ -83,4 +83,12 @@ resources:
   kind: SetupKey
   path: github.com/netbirdio/kubernetes-operator/api/v1alpha1
   version: v1alpha1
+- api:
+    crdVersion: v1
+    namespaced: true
+  controller: true
+  domain: netbird.io
+  kind: Group
+  path: github.com/netbirdio/kubernetes-operator/api/v1alpha1
+  version: v1alpha1
 version: "3"