@Override
    public InstanceIdentity refreshInstance(AthenzIdentity providerIdentity,
                                            AthenzIdentity instanceIdentity,
                                            String instanceId,
                                            Pkcs10Csr csr) {
        InstanceRefreshInformation payload = new InstanceRefreshInformation(csr);
        URI uri = ztsUrl.resolve(
                String.format("instance/%s/%s/%s/%s",
                              providerIdentity.getFullName(),
                              instanceIdentity.getDomain().getName(),
                              instanceIdentity.getName(),
                              instanceId));
        HttpUriRequest request = RequestBuilder.post()
                .setUri(uri)
                .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