anchor.diff:  
           server {
             listen ${listenString};
  -          listen [::]:${listenString};
  +          ${optionalString enableIPv6 "listen [::]:${listenString};"}
   
             server_name ${serverName} ${concatStringsSep " " vhost.serverAliases};
             ${acmeLocation}
  
positive.code:       ${optionalString cfg.statusPage ''
          server {
            listen 80;
            listen [::]:80;
  
            server_name localhost;
  
  
negative.code:             stub_status on;
              access_log off;
              allow 127.0.0.1;
              ${optionalString enableIPv6 "allow ::1;"}
              deny all;
            }
          }
  