docs: public long getResponseContentLength() {
          Header[] headers = getResponseHeaderGroup().getHeaders("Content-Length");
          if (headers.length == 0) {
              return -1;
          }
          if (headers.length > 1) {
              LOG.warn("Multiple content-length headers detected");
          }
          for (int i = headers.length - 1; i >= 0; i--) {
              Header header = headers[i];
              try {
                  return Long.parseLong(header.getValue());
              } catch (NumberFormatException e) {
                  if (LOG.isWarnEnabled()) {
                      LOG.warn("Invalid content-length value: " + e.getMessage());
                  }
              }
              // See if we can have better luck with another header, if present
          }
          return -1;
      }