code: public JsPayResponse jsPay(JsPayRequest request){
          checkJsPayParams(request);
          Map<String, Object> respData = doJsPay(request, TradeType.JSAPI);
          return buildJsPayResp(respData);
      }
docs: JS支付(公众号支付)
  @param request 支付请求对象
  @return JsPayResponse对象，或抛WepayException