public static final String X_POWERED_BY = "X-Powered-By";
  /**
   * The HTTP <a href="http://tools.ietf.org/html/draft-evans-palmer-key-pinning">{@code
   * Public-Key-Pins}</a> header field name.
   *
   * @since 15.0
   */
  public static final String PUBLIC_KEY_PINS = "Public-Key-Pins";
  /**
   * The HTTP <a href="http://tools.ietf.org/html/draft-evans-palmer-key-pinning">{@code

   * is complete. It does so by using daemon threads and adding a shutdown hook to wait for their
   * completion.
   *
   * <p>This is mainly for fixed thread pools. See {@link Executors#newFixedThreadPool(int)}.
   *
   * @param executor the executor to modify to make sure it exits when the application is finished