private void addIdentityProvider(ApplicationContainerCluster cluster, List<ConfigServerSpec> configServerSpecs, HostName loadBalancerName,
                                     URI ztsUrl, String athenzDnsSuffix, Zone zone, DeploymentSpec spec) {
        spec.athenzDomain().ifPresent(domain -> {
            AthenzService service = spec.athenzService(app.getApplicationId().instance(), zone.environment(), zone.region())
                                        .orElseThrow(() -> new IllegalArgumentException("Missing Athenz service configuration in instance '" +
                                                                                        app.getApplicationId().instance() + "'"));
            addIdentityProvider(cluster, configServerSpecs, loadBalancerName, ztsUrl, athenzDnsSuffix, zone, domain, service);
        });
    }
Allocate a container cluster without a nodes tag
config-model/src/main/java/com/yahoo/vespa/model/container/xml/ContainerModelBuilder.java