tt-rss: don't hard-code nginx user in service

        inherit (cfg) user;

        inherit phpPackage;

        settings = mapAttrs (name: mkDefault) {

          "listen.owner" = "nginx";

          "listen.group" = "nginx";

          "listen.owner" = config.services.nginx.user;

          "listen.group" = config.services.nginx.group;

          "listen.mode" = "0600";

          "pm" = "dynamic";

          "pm.max_children" = 75;