private boolean canUpgradeWithinDeadline(Instant instant) {
        instant = instant.truncatedTo(ChronoUnit.HOURS);
        Duration step = Duration.ofHours(1);
        Duration max = Duration.ofDays(maxUpgradeBlockingDays);
        for (Instant current = instant; ! canUpgradeAt(current); current = current.plus(step)) {
            Duration blocked = Duration.between(instant, current);
            if (blocked.compareTo(max) > 0) {
                return false;
            }
        }
        return true;
    }
Returns whether this allows upgrade within deadline, relative to given instant
config-model-api/src/main/java/com/yahoo/config/application/api/DeploymentInstanceSpec.java