public static ApplicationInstanceId toApplicationInstanceId(ApplicationId applicationId, Zone zone) {
        if (applicationId.equals(configServerApplicationId)) {
            // Removing this historical discrepancy would break orchestration during rollout.
            // An alternative may be to use a feature flag and flip it between releases,
            // once that's available.
            return new ApplicationInstanceId(applicationId.application().value());
        } else {
            return new ApplicationInstanceId(String.format("%s:%s:%s:%s",
                    applicationId.application().value(),
                    zone.environment().value(),
                    zone.region().value(),
                    applicationId.instance().value()));
        }
    }
Reverse of toApplicationInstanceId, put in this file because it its inverse is.
service-monitor/src/main/java/com/yahoo/vespa/service/model/ApplicationInstanceGenerator.java