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/health/HealthIndicatorServiceTests.java
impacts.add(impact2);
        impacts.add(impact1);
        impacts.add(impact3);
        for (int i = 0; i < 10; i++) {
            impacts.add(new HealthIndicatorImpact(randomIntBetween(5, 20), randomAlphaOfLength(20)));
        }
        HealthIndicatorResult result = service.createIndicator(status, randomAlphaOfLength(20), HealthIndicatorDetails.EMPTY, impacts);
        List<HealthIndicatorImpact> outputImpacts = result.impacts();
        assertEquals(3, outputImpacts.size());
        List<HealthIndicatorImpact> expectedImpacts = List.of(impact1, impact2, impact3);
        assertEquals(expectedImpacts, outputImpacts);
    }
    private HealthIndicatorService getTestHealthIndicatorService() {
        return new HealthIndicatorService() {
            @Override
            public String name() {
                return null;
            }
            @Override
            public String component() {
                return null;
            }
            @Override
            public HealthIndicatorResult calculate(boolean calculateDetails) {
                return null;
            }
        };
    }
}