private String calculateNonce() {
        val time = LocalDateTime.now();
        val formatter = DateTimeFormatter.ofPattern("yyyy:MM:dd:HH:mm:ss.SSS");
        val fmtTime = formatter.format(time);
        return CredentialUtil.encryptMD5(fmtTime + CommonHelper.randomString(10));
    }
A server-specified data string which should be uniquely generated each time a 401 response is made (RFC 2617)
Based on current time including nanoseconds
pac4j-http/src/main/java/org/pac4j/http/client/direct/DirectDigestAuthClient.java