use ARG ENV to chown /code for prod to allow gunicorn logs to work in prod as non-root user

Dockerfile

@@ -3,11 +3,15 @@ WORKDIR /code
 COPY . .
 
 # declare var
+ARG ENV
 ARG BOOK_UID
 ARG BOOK_GID
 
-WORKDIR /code
 RUN groupadd -g ${BOOK_GID} pybook && useradd -m -u ${BOOK_UID} -g ${BOOK_GID} pybook
+# in prod, /code will be owned by root and gunicorn logs wont work, so chg to pybook
+RUN if [ "$ENV" = "production" ]; then \
+        chown -R pybook:pybook /code; \
+    fi
 
 RUN wget https://dl.google.com/linux/direct/google-chrome-stable_current_amd64.deb
 RUN apt-get update && \