Result result() {
            var intersection = new HashSet<>(implicitlyMaintained);
            intersection.retainAll(implicitlyDown);
            if (intersection.size() > 0) {
                throw new IllegalStateException("Nodes implicitly both maintenance and down: " + intersection);
            }

            return new Result(implicitlyMaintained, implicitlyDown);
        }
If the number of nodes safely set to maintenance is at least this number, the remaining
nodes in the group will be set to maintenance (storage nodes) or down (distributors).

<p>This feature is disabled if safeMaintenanceGroupThreshold is 0 (not default).</p>
clustercontroller-core/src/main/java/com/yahoo/vespa/clustercontroller/core/GroupAvailabilityCalculator.java