private static Optional<String> getAthenzUniqueInstanceIdFromSanDns(List<SubjectAlternativeName> sans) {
        String dnsNameDelimiter = ".instanceid.athenz.";
        return sans.stream()
                .filter(san -> {
                    if (san.getType() != Type.DNS) return false;
                    return san.getValue().contains(dnsNameDelimiter);
                })
                .map(san -> {
                    String dnsName = san.getValue();
                    return dnsName.substring(0, dnsName.indexOf(dnsNameDelimiter));
                })
                .findFirst();
    }
@return Athenz URI hostname from the Subject Alternative Name extension
vespa-athenz/src/main/java/com/yahoo/vespa/athenz/tls/AthenzX509CertificateUtils.java