Because we are using openwrt and we would like to mantain LUCI running
on it's interface we can't bind on 0.0.0.0. or 127.0.0.1 hence we must
listen on a specific ip. This will set the public ip from the group
vars to be the one where we listen

The server, map and upstream directives can be splitted into
different files to be included into the nginx.conf configuration.