anchor.diff:        }
         { assertion = cfg.database.createLocally -> cfg.database.passwordFile == null;
           message = ''services.invoiceplane.sites."${hostName}".database.passwordFile cannot be specified if services.invoiceplane.sites."${hostName}".database.createLocally is set to true.'';
  -      }]
  -    ) eachSite);
  +      }
  +      { assertion = cfg.cron.enable -> cfg.cron.key != null;
  +        message = ''services.invoiceplane.sites."${hostName}".cron.key must be set in order to use cron service.'';
  +      }
  +    ]) eachSite);
   
       services.mysql = mkIf (any (v: v.database.createLocally) (attrValues eachSite)) {
         enable = true;
  
positive.code:     };
    })
  
  
    ]);
  }
  
negative.code:   }
  
    {
  
      systemd.tmpfiles.rules = flatten (mapAttrsToList (hostName: cfg: [
        "d ${cfg.stateDir} 0750 ${user} ${webserver.group} - -"
        "f ${cfg.stateDir}/ipconfig.php 0750 ${user} ${webserver.group} - -"
  