Proxying Server from Apache on Synology

How to redirect a part of your web site to another server on your LAN:

... On your NAS: at the bottom of /usr/syno/apache/conf/httpd.conf-user

ProxyRequests Off
<proxy *>
  Order deny,allow
  Allow from all
</proxy>
ProxyPass /redmine http://192.168.0.78/redmine
ProxyPassReverse /redmine http://192.168.0.78/redmine
<location redmine>
  AuthName "Protected Access"
  AuthType Basic
  AuthUserFile /var/services/web/hg/.htpasswd
  require valid-user
</location>

It tells Apache to redirect all /redmine/* access to another server (this subdirectory is protected by password in this case).

And... That's all :)