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/HealthIndicatorResultTests.java
Map<String, Object> detailsMap = new HashMap<>();
        detailsMap.put("key", "value");
        HealthIndicatorDetails details = new SimpleHealthIndicatorDetails(detailsMap);
        List<HealthIndicatorImpact> impacts = new ArrayList<>();
        int impact1Severity = randomIntBetween(1, 5);
        String impact1Description = randomAlphaOfLength(30);
        impacts.add(new HealthIndicatorImpact(impact1Severity, impact1Description));
        int impact2Severity = randomIntBetween(1, 5);
        String impact2Description = randomAlphaOfLength(30);
        impacts.add(new HealthIndicatorImpact(impact2Severity, impact2Description));
        HealthIndicatorResult result = new HealthIndicatorResult(name, component, status, summary, details, impacts);
        XContentBuilder builder = XContentFactory.jsonBuilder().prettyPrint();
        result.toXContent(builder, ToXContent.EMPTY_PARAMS);
        Map<String, Object> xContentMap = XContentHelper.convertToMap(BytesReference.bytes(builder), false, builder.contentType()).v2();
        assertEquals(status.xContentValue(), xContentMap.get("status"));
        assertEquals(summary, xContentMap.get("summary"));
        assertEquals(detailsMap, xContentMap.get("details"));
        List<Map<String, Object>> expectedImpacts = new ArrayList<>();
        Map<String, Object> expectedImpact1 = new HashMap<>();
        expectedImpact1.put("severity", impact1Severity);
        expectedImpact1.put("description", impact1Description);
        Map<String, Object> expectedImpact2 = new HashMap<>();
        expectedImpact2.put("severity", impact2Severity);
        expectedImpact2.put("description", impact2Description);
        expectedImpacts.add(expectedImpact1);
        expectedImpacts.add(expectedImpact2);
        assertEquals(expectedImpacts, xContentMap.get("impacts"));
    }
}