@Override
    public Identity getServiceIdentity(AthenzIdentity identity, String keyId, Pkcs10Csr csr) {
        return getServiceIdentity(identity, keyId, csr, Optional.empty());
    }
Default implementation of {@link ZtsClient}

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