code: public Map<String, Object> refundOrder(String orderId, Setup setup) {
          this.requestMaker = new RequestMaker(setup);
          RequestProperties props = new RequestPropertiesBuilder()
                  .method("POST")
                  .endpoint(String.format(ENDPOINT_REFUND_ORDER, orderId))
                  .type(Refunds.class)
                  .contentType(CONTENT_TYPE)
                  .build();
  
          return this.requestMaker.doRequest(props);
      }
docs: This method is used to create a order refund without request body.
  TIP: Actually, its possible make only refund by credit card with this method.
  
  @param   orderId
  {@code String} the Moip order external ID.
  
  @param   setup
  {@code Setup} the setup object.
  
  @return  {@code Map<String, Object>}