Fix reverse proxy Dockerfile

- Point to correct image names
- Add a SECRET_KEY environment variable while executing collectstatic

Author: cache-rules

docker/reverse_proxy/Dockerfile

@@ -1,7 +1,7 @@
-FROM nerd_herder_frontend:latest as frontend
+FROM registry.gitlab.com/cache-rules/nerd_herder_ops/frontend:latest as frontend
 RUN yarn build
-FROM nerd_herder_nerd_herder:latest as backend
-RUN python manage.py collectstatic --no-input
+FROM registry.gitlab.com/cache-rules/nerd_herder_ops/nerd_herder:latest as backend
+RUN SECRET_KEY=WORKAROUND_FOR_COLLECTSTATIC python manage.py collectstatic --no-input
 FROM abiosoft/caddy:0.11.0-no-stats
 
 COPY --from=frontend /usr/src/nerd_herder/frontend/build /var/www/nerd_herder/