code: private static Response join(final Response response) throws IOException {
          final StringBuilder cookies = new StringBuilder();
          for (final String header : response.head()) {
              final Matcher matcher =
                  TkJoinedCookies.PTN.matcher(header);
              if (!matcher.matches()) {
                  continue;
              }
              cookies.append(matcher.group(1)).append(", ");
          }
          final Response out;
          if (cookies.length() > 0) {
              out = new RsWithHeader(
                  new RsWithoutHeader(response, "Set-cookie"),
                  "Set-Cookie", cookies.toString()
              );
          } else {
              out = response;
          }
          return out;
      }
docs: Join them.
  @param response The response
  @return New response
  @throws IOException If fails