protected long currentTimeMillis() {
      return System.currentTimeMillis();
    }
Decodes a {@link feign.Util#RETRY_AFTER} header into an epoch millisecond, if possible.<br>
See <a href="https://tools.ietf.org/html/rfc2616#section-14.37">Retry-After format</a>
core/src/main/java/feign/codec/ErrorDecoder.java