code: @Override
      public NutMap send_redpackgroup(String key, WxPayRedPackGroup wxRedPackGroup, File file, String password) {
          String url = payBase + "/mmpaymkttransfers/sendgroupredpack";
          Map<String, Object> params = Lang.obj2map(wxRedPackGroup);
          return this.postPay(url, key, params, file, password);
      }
docs: 发送裂变红包
  
  @param key
  商户KEY
  @param wxRedPackGroup
  红包内容
  @param file
  证书文件
  @param password
  证书密码
  @return