nixos/modules: add option for omnom's base_url setting

                  "127.0.0.1:''${config.services.omnom.port}"

                '';

              };

              # NOTE: this can't be empty, because it will be overwritten by

              # Omnom's internal default config.

              base_url = lib.mkOption {

                type = lib.types.str;

                internal = true;

                default = "http://127.0.0.1:${toString cfg.port}/";

                description = "Full server URL.";

                example = "https://local.omnom/xy/";

                defaultText = lib.literalExpression ''

                  "http://''${config.services.omnom.settings.server.address}/"

                '';

              };

              secure_cookie = lib.mkOption {

                type = lib.types.bool;

                default = true;