As we are rolling out the user profile feature, we'd like to expand the [Usage API](https://www.elastic.co/guide/en/elasticsearch/reference/current/usage-api.html) to report usage stats of user profiles such as (1) number of enabled user profiles and (2) number of user profiles that are [activated](https://www.elastic.co/guide/en/elasticsearch/reference/current/security-api-activate-user-profile.html) over the past X days. 

Response of the Usage API already contains a `security` field that groups relevant stats from security related features. We expect the new stats for user profiles should be added under it as well, for example:
```
{
  "security: {
    "user_profile": {
      "activated": 78,
      "recently_activated": 42  <1>
    }
  }
}
```
<1> The use of `recently_` is chosen to avoid the field to be tied to a specific time period so it is easier to evolve the definition in future.

x-pack/plugin/security/src/test/java/org/elasticsearch/xpack/security/SecurityInfoTransportActionTests.java
}
        }
    }
    private XContentSource getXContentSource(XPackFeatureSet.Usage usage) throws IOException {
        XContentSource source;
        try (XContentBuilder builder = XContentFactory.jsonBuilder()) {
            usage.toXContent(builder, ToXContent.EMPTY_PARAMS);
            source = new XContentSource(builder);
        }
        return source;
    }
    private void configureRealmsUsage(Map<String, Object> realmsUsageStats) {
        doAnswer(invocationOnMock -> {
            @SuppressWarnings("unchecked")
            ActionListener<Map<String, Object>> listener = (ActionListener<Map<String, Object>>) invocationOnMock.getArguments()[0];
            listener.onResponse(realmsUsageStats);
            return Void.TYPE;
        }).when(realms).usageStats(anyActionListener());
    }
    private void configureRoleStoreUsage(boolean rolesStoreEnabled) {
        doAnswer(invocationOnMock -> {
            @SuppressWarnings("unchecked")
            ActionListener<Map<String, Object>> listener = (ActionListener<Map<String, Object>>) invocationOnMock.getArguments()[0];
            if (rolesStoreEnabled) {
                listener.onResponse(Collections.singletonMap("count", 1));
            } else {
                listener.onResponse(Collections.emptyMap());
            }
            return Void.TYPE;
        }).when(rolesStore).usageStats(anyActionListener());