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
it -> SingleNodeShutdownMetadata.builder()
                            .setNodeId(it.nodeId)
                            .setType(it.type)
                            .setReason("test")
                            .setNodeSeen(true)
                            .setStartedAtMillis(System.currentTimeMillis())
                            .setAllocationDelay(it.allocationDelaySeconds != null ? timeValueSeconds(it.allocationDelaySeconds) : null)
                            .build()
                    )
                )
        );
        Metadata.Builder metadataBuilder = Metadata.builder();
        ImmutableOpenMap.Builder<String, IndexMetadata> indexMetadataMapBuilder = ImmutableOpenMap.builder();
        for (IndexMetadata indexMetadata : indexMetadataList) {
            indexMetadataMapBuilder.put(indexMetadata.getIndex().getName(), indexMetadata);
        }
        metadataBuilder.indices(indexMetadataMapBuilder.build());
        metadataBuilder.putCustom(NodesShutdownMetadata.TYPE, nodesShutdownMetadata);
        return ClusterState.builder(new ClusterName("test-cluster"))
            .routingTable(routingTableBuilder.build())
            .metadata(metadataBuilder.build())
            .build();
    }
    private static Map<String, Object> addDefaults(Map<String, Object> override) {
        return Map.of(
            "unassigned_primaries",
            override.getOrDefault("unassigned_primaries", 0),
            "initializing_primaries",
            override.getOrDefault("initializing_primaries", 0),
            "creating_primaries",