nixos/mailman: configure web frontend with postfix when enablePostfix… (#333295)

      ENGINE = "haystack.backends.whoosh_backend.WhooshEngine";

      PATH = "/var/lib/mailman-web/fulltext-index";

    };

  } // lib.optionalAttrs cfg.enablePostfix {

    EMAIL_BACKEND = "django.core.mail.backends.smtp.EmailBackend";

    EMAIL_HOST = "127.0.0.1";

    EMAIL_PORT = 25;

  } // cfg.webSettings;

  webSettingsJSON = pkgs.writeText "settings.json" (builtins.toJSON webSettings);