Reverse Proxy Dockerfile: Use build args for image versions

Now staging and prod docker-compose files specify the image versions to
be used inside the reverse-proxy image.

Author: cache-rules

docker-compose.prod.yml

@@ -45,7 +45,10 @@ services:
     build:
       context: .
       dockerfile: docker/reverse_proxy/Dockerfile
-    image: registry.gitlab.com/cache-rules/nerd_herder_ops/reverse_proxy:0.10
+      args:
+        FRONTEND_IMAGE: registry.gitlab.com/cache-rules/nerd_herder_ops/frontend:0.6
+        BACKEND_IMAGE: registry.gitlab.com/cache-rules/nerd_herder_ops/nerd_herder:0.8
+    image: registry.gitlab.com/cache-rules/nerd_herder_ops/reverse_proxy:0.11
     deploy:
       replicas: 1
       restart_policy:

docker-compose.staging.yml

@@ -48,7 +48,10 @@ services:
     build:
       context: .
       dockerfile: docker/reverse_proxy/Dockerfile
-    image: registry.gitlab.com/cache-rules/nerd_herder_ops/reverse_proxy:0.9-beta
+      args:
+        FRONTEND_IMAGE: registry.gitlab.com/cache-rules/nerd_herder_ops/frontend:0.6-beta
+        BACKEND_IMAGE: registry.gitlab.com/cache-rules/nerd_herder_ops/nerd_herder:0.8-beta
+    image: registry.gitlab.com/cache-rules/nerd_herder_ops/reverse_proxy:0.11-beta
     deploy:
       replicas: 1
       restart_policy:

docker/reverse_proxy/Dockerfile

@@ -1,7 +1,12 @@
-FROM registry.gitlab.com/cache-rules/nerd_herder_ops/frontend:0.6 as frontend
+ARG FRONTEND_IMAGE=registry.gitlab.com/cache-rules/nerd_herder_ops/frontend:latest
+ARG BACKEND_IMAGE=registry.gitlab.com/cache-rules/nerd_herder_ops/nerd_herder:latest
+
+FROM ${FRONTEND_IMAGE} as frontend
 RUN yarn build
-FROM registry.gitlab.com/cache-rules/nerd_herder_ops/nerd_herder:0.8 as backend
+
+FROM ${BACKEND_IMAGE} as backend
 RUN SECRET_KEY=WORKAROUND_FOR_COLLECTSTATIC python manage.py collectstatic --no-input
+
 FROM abiosoft/caddy:1.0.0-no-stats
 
 COPY --from=frontend /usr/src/nerd_herder/frontend/build /var/www/nerd_herder/