public Set<ApplicationInstanceReference> toApplicationInstanceReferenceSet(List<ApplicationInfo> infos) {
        return infos.stream()
                .map(info -> new ApplicationInstanceGenerator(info, zone).toApplicationInstanceReference())
                .collect(Collectors.toSet());
    }
Create service model based primarily on super model.

If the configServerhosts is non-empty, a config server application is added.
service-monitor/src/main/java/com/yahoo/vespa/service/model/ModelGenerator.java