code: public HttpResponse withBody(String body, Charset charset) {
          if (body != null) {
              this.body = new StringBody(body, charset);
          }
          return this;
      }
docs: Set response body to return a string response body with the specified encoding. <b>Note:</b> The character set of the
  response will be forced to the specified charset, even if the Content-Type header specifies otherwise.
  
  @param body    a string
  @param charset character set the string will be encoded in