eg
```
"impacts": [
            {
              "severity": 3,
              "description": "Searches might return slower than usual. Fewer redundant copies of the data exist on 2 indices [.ds-logslogslogs-2022.03.29-000001, my-index-000001].",
              "impact_areas": [ "search" ]
            }
          ]
```
server/src/main/java/org/elasticsearch/cluster/routing/allocation/ShardsAvailabilityHealthIndicatorService.java
}
        public void addPrimary(ShardRouting routing, NodesShutdownMetadata shutdowns) {
            primaries.increment(routing, shutdowns);
        }
        public void addReplica(ShardRouting routing, NodesShutdownMetadata shutdowns) {
            replicas.increment(routing, shutdowns);
        }
        public HealthStatus getStatus() {
            if (primaries.available == false) {
                return RED;
            } else if (replicas.available == false) {
                return YELLOW;
            } else {
                return GREEN;
            }
        }
        public String getSummary() {
            var builder = new StringBuilder("This cluster has ");
            if (primaries.unassigned > 0
                || primaries.unassigned_new > 0
                || primaries.unassigned_restarting > 0
                || replicas.unassigned > 0
                || replicas.unassigned_restarting > 0) {
                builder.append(
                    Stream.of(
                        createMessage(primaries.unassigned, "unavailable primary", " unavailable primaries"),
                        createMessage(primaries.unassigned_new, "creating primary", " creating primaries"),
                        createMessage(primaries.unassigned_restarting, "restarting primary", " restarting primaries"),
                        createMessage(replicas.unassigned, "unavailable replica", "unavailable replicas"),
                        createMessage(replicas.unassigned_restarting, "restarting replica", "restarting replicas")