@Override
    public X509Certificate getRoleCertificate(AthenzRole role, Pkcs10Csr csr) {
        return getRoleCertificate(role, csr, null);
    }
Default implementation of {@link ZtsClient}

@author bjorncs
@author mortent
vespa-athenz/src/main/java/com/yahoo/vespa/athenz/client/zts/DefaultZtsClient.java