feat: allow for custom registry

This patch adds a simple CLI which can mirror all the images needed
as well as allow for simple override for `atmosphere_image_repository`
for all images.
diff --git a/roles/coredns/tasks/main.yml b/roles/coredns/tasks/main.yml
index cda29f0..dceb12b 100644
--- a/roles/coredns/tasks/main.yml
+++ b/roles/coredns/tasks/main.yml
@@ -31,6 +31,8 @@
                 kind: HelmRepository
                 name: coredns
           values:
+            image:
+              repository: "{{ lookup('vexxhost.atmosphere.image_ref', 'neutron_coredns', output='name') }}"
             replicaCount: 3
             prometheus:
               service: