build: add missing atlantis user in Debian image (runatlantis#3317)

It appears that when runatlantis#3001 combined the Dockerfiles, the bit that adds
the `atlantis` user was not added to the Debian build stage

Also correct some trailing spaces and missing EOL in
`docker-compose.yml`

Dockerfile

@@ -179,6 +179,13 @@ CMD ["server"]
 # Stage 2 - Debian
 FROM debian:${DEBIAN_TAG} AS debian
 
+# Add atlantis user to Debian as well
+RUN useradd --create-home --user-group --shell /bin/bash atlantis && \
+    adduser atlantis root && \
+    chown atlantis:root /home/atlantis/ && \
+    chmod g=u /home/atlantis/ && \
+    chmod g=u /etc/passwd
+
 # copy binary
 COPY --from=builder /app/atlantis /usr/local/bin/atlantis
 # copy terraform

docker-compose.yml

@@ -20,7 +20,7 @@ services:
         ports:
         - '6379:6379'
         command: redis-server --save 20 1 --loglevel warning --requirepass test123
-        volumes: 
+        volumes:
         - redis:/data
     atlantis:
         depends_on: