public Autoscaling asIdeal(Instant at) {
        return new Autoscaling(Status.ideal,
                               "Cluster is ideally scaled within configured limits",
                               Optional.empty(),
                               at,
                               peak,
                               ideal,
                               metrics);
    }
Converts this autoscaling into an ideal one at the completion of it.
node-repository/src/main/java/com/yahoo/vespa/hosted/provision/autoscale/Autoscaling.java