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>

helm/kubernetes-operator/crds/netbird.io_setupkeys.yaml

@@ -39,6 +39,34 @@ spec:
           spec:
             description: spec defines the desired state of SetupKey
             properties:
+              autoGroups:
+                description: Groups that will be automatically assigned to resources
+                  using setup key.
+                items:
+                  properties:
+                    id:
+                      description: id of the resource in the Netbird API.
+                      type: string
+                    localRef:
+                      description: local reference to the object in the same namespace.
+                      properties:
+                        name:
+                          default: ""
+                          description: |-
+                            Name of the referent.
+                            This field is effectively required, but due to backwards compatibility is
+                            allowed to be empty. Instances of this type with an empty value here are
+                            almost certainly wrong.
+                            More info: https://kubernetes.io/docs/concepts/overview/working-with-objects/names/#names
+                          type: string
+                      type: object
+                      x-kubernetes-map-type: atomic
+                  type: object
+                  x-kubernetes-validations:
+                  - message: exactly one of id or localRef must be set
+                    rule: (has(self.id) && !has(self.localRef)) || (!has(self.id)
+                      && has(self.localRef))
+                type: array
               duration:
                 description: Duration sets how long the setup key is valid for.
                 type: string