@Override
    public InstanceIdentity registerInstance(AthenzIdentity providerIdentity,
                                             AthenzIdentity instanceIdentity,
                                             String attestationData,
                                             Pkcs10Csr csr) {
        InstanceRegisterInformation payload =
                new InstanceRegisterInformation(providerIdentity, instanceIdentity, attestationData, csr);
        HttpUriRequest request = RequestBuilder.post()
                .setUri(ztsUrl.resolve("instance/"))
                .setEntity(toJsonStringEntity(payload))
                .build();
        return execute(request, this::getInstanceIdentity);
    }
Default implementation of {@link ZtsClient}

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