Changes in posting constraints due to rescoping to OCP/K8S-only

- node_state is now read only
- node_state gets set automatically to Installed in the create view
- raise a validation error when creating on non-K8S
- allow SystemAdministrator the 'add' permission for Instances
- expose the new listener_port field

awx/api/views/__init__.py

@@ -367,6 +367,9 @@ class InstanceList(ListCreateAPIView):
     search_fields = ('hostname',)
     ordering = ('id',)
 
+    def perform_create(self, serializer):
+        serializer.save(node_state=models.Instance.States.INSTALLED)
+
 
 class InstanceDetail(RetrieveUpdateAPIView):