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/test/java/org/elasticsearch/cluster/routing/allocation/ShardsAvailabilityHealthIndicatorServiceTests.java
override.getOrDefault("creating_primaries", 0),
            "restarting_primaries",
            override.getOrDefault("restarting_primaries", 0),
            "started_primaries",
            override.getOrDefault("started_primaries", 0),
            "unassigned_replicas",
            override.getOrDefault("unassigned_replicas", 0),
            "initializing_replicas",
            override.getOrDefault("initializing_replicas", 0),
            "restarting_replicas",
            override.getOrDefault("restarting_replicas", 0),
            "started_replicas",
            override.getOrDefault("started_replicas", 0)
        );
    }
    private static IndexRoutingTable index(String name, ShardAllocation primaryState, ShardAllocation... replicaStates) {
        var index = new Index(name, UUID.randomUUID().toString());
        var shardId = new ShardId(index, 0);
        var builder = IndexRoutingTable.builder(index);
        builder.addShard(createShardRouting(shardId, true, primaryState));
        for (var replicaState : replicaStates) {
            builder.addShard(createShardRouting(shardId, false, replicaState));
        }
        return builder.build();
    }
    private static ShardRouting createShardRouting(ShardId shardId, boolean primary, ShardAllocation allocation) {
        var routing = newUnassigned(
            shardId,
            primary,
            getSource(primary, allocation.state),