ci: add full-node tests (#920)

diff --git a/images/magnum/Earthfile b/images/magnum/Earthfile
index b3d386c..52e0ac5 100644
--- a/images/magnum/Earthfile
+++ b/images/magnum/Earthfile
@@ -1,5 +1,6 @@
 VERSION 0.7
 
+ARG --global REGISTRY=ghcr.io/vexxhost/atmosphere
 ARG --global PROJECT=magnum
 ARG --global RELEASE=2023.2
 ARG --global PROJECT_REF=156f6f52d38a670e6fe10725966aeea4ddf65146
@@ -18,5 +19,5 @@
     --PACKAGES "haproxy"
   COPY ../helm+binary/helm /usr/local/bin/helm
   SAVE IMAGE --push \
-    ghcr.io/vexxhost/atmosphere/${PROJECT}:${RELEASE} \
-    ghcr.io/vexxhost/atmosphere/${PROJECT}:${PROJECT_REF}
+    ${REGISTRY}/${PROJECT}:${RELEASE} \
+    ${REGISTRY}/${PROJECT}:${PROJECT_REF}