nixos/patroni: fix documentation link for settings and add example (#441713)

    settings = lib.mkOption {

      type = format.type;

      default = { };

      example = {

        bootstrap = {

          initdb = [

            "encoding=UTF-8"

            "data-checksums"

          ];

        };

        postgresql = {

          parameters = {

            unix_socket_directories = "/tmp";

          };

        };

      };

      description = ''

        The primary patroni configuration. See the [documentation](https://patroni.readthedocs.io/en/latest/SETTINGS.html)

        The primary patroni configuration. See the [documentation](https://patroni.readthedocs.io/en/latest/yaml_configuration.html)

        for possible values.

        Secrets should be passed in by using the `environmentFiles` option.

      '';