In some contexts is unclear why an autoscaling policy decides to request
more resources, i.e. if there's an unassigned shard that remains unassigned
even after adding more resources. It would be help to have more information
around the decisions taken by the deciders so it is easier to understand and
track them.
x-pack/plugin/autoscaling/src/main/java/org/elasticsearch/xpack/autoscaling/storage/ReactiveStorageDeciderService.java
private final String reason;
        private final long unassigned;
        private final long assigned;
        public ReactiveReason(String reason, long unassigned, long assigned) {
            this.reason = reason;
            this.unassigned = unassigned;
            this.assigned = assigned;
        }
        public ReactiveReason(StreamInput in) throws IOException {
            this.reason = in.readString();
            this.unassigned = in.readLong();
            this.assigned = in.readLong();
        }
        @Override
        public String summary() {
            return reason;
        }
        public long unassigned() {
            return unassigned;
        }
        public long assigned() {
            return assigned;
        }
        @Override
        public String getWriteableName() {
            return ReactiveStorageDeciderService.NAME;