anchor.diff:  
     config = mkIf cfg.enable {
   
  -    services.postgresql.enable = cfg.dbServer == "localhost";
  +    services.postgresql.enable = useLocalPostgres;
   
       users.extraUsers = singleton
         { name = "zabbix";
  
positive.code:       ''}
      '';
  
  in
  
  {
  
negative.code: 
      services.zabbixServer.dbServer = mkOption {
        default = "localhost";
        description = ''
          Hostname or IP address of the database server.
          Use an empty string ("") to use peer authentication.
        '';
      };
  
      services.zabbixServer.dbPassword = mkOption {
  