Relax9 issues

Results 3 issues of


                                            Relax9

v3接口在Spring Boot Jar包模式下无法读取证书

### 版本信息 - IJPay 版本: 2.7.5 - 开发环境: Linux - 支付方式: 微信支付 - ### 报错信息（注意格式化） ``` IJPayHttpResponse response = WxPayApi.v3( RequestMethod.POST, WxDomain.CHINA.toString(), WxApiType.JS_API_PAY.toString(), wechatPaymentPlatform.getMchId(), getSerialNumber(wechatPaymentPlatform), null, wechatPaymentPlatform.getApiClientKeyPath(), JSONUtil.toJsonStr(unifiedOrderModel) cn.hutool.core.io.IORuntimeException:...

希望能添加一个持续发送的功能

因为很多场景是需要持续接收数据来完成的，希望能加上这个功能

父类的枚举类型无法被mock

![image](https://user-images.githubusercontent.com/21021062/106568076-be17bf00-656d-11eb-905f-44ba2fa682d8.png) ![image](https://user-images.githubusercontent.com/21021062/106568114-cbcd4480-656d-11eb-89af-1a16ddfd5a43.png) ![image](https://user-images.githubusercontent.com/21021062/106568130-d4257f80-656d-11eb-9b54-0d46bb405220.png)