Another Apache2 reverse proxy fix, thanks Elvir

docs/first_steps.md

@@ -99,7 +99,7 @@ Recreate affected containers by running `docker-compose up -d`.
     # You should proxy to a plain HTTP session to offload SSL processing
     ProxyPass / http://127.0.0.1:8080/
     ProxyPassReverse / http://127.0.0.1:8080/
-    ProxyPreserveHost On
+    ProxyPreserveHost Off
     your-ssl-configuration-here
     [...]