Simplify forum container configuration

Forum environment variables no longer need to be defined in
docker-compose. Instead, the default values defined at build time are
used.

build/forum/Dockerfile

@@ -29,5 +29,8 @@ RUN bundle install --deployment
 
 ENV RACK_ENV staging
 ENV NEW_RELIC_ENABLE false
+ENV API_KEY forumapikey
+ENV SEARCH_SERVER "http://elasticsearch:9200"
+ENV MONGOHQ_URL "mongodb://mongodb/cs_comments_service"
 EXPOSE 4567
 CMD ./bin/unicorn -c config/unicorn_tcp.rb -I '.'

deploy/local/templates/docker-compose.yml

@@ -67,10 +67,6 @@ services:
 
   forum:
     image: regis/openedx-forum:hawthorn
-    environment:
-      API_KEY: "forumapikey"
-      SEARCH_SERVER: "http://elasticsearch:9200"
-      MONGOHQ_URL: "mongodb://mongodb/cs_comments_service"
     restart: unless-stopped
     depends_on:
       - elasticsearch