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/main/java/org/elasticsearch/xpack/security/profile/ProfileService.java
doc.applicationData()
        );
    }
    
    record VersionedDocument(ProfileDocument doc, long primaryTerm, long seqNo) {
        /**
         * Convert the index document to the user-facing Profile by filtering through the application data
         */
        Profile toProfile(Set<String> dataKeys) {
            assert dataKeys != null : "data keys must not be null";
            final Map<String, Object> applicationData;
            if (dataKeys.isEmpty()) {
                applicationData = Map.of();
            } else {
                applicationData = XContentHelper.convertToMap(doc.applicationData(), false, XContentType.JSON, dataKeys, null).v2();
            }
            return new Profile(
                doc.uid(),
                doc.enabled(),
                doc.lastSynchronized(),
                doc.user().toProfileUser(),
                doc.labels(),
                applicationData,
                new Profile.VersionControl(primaryTerm, seqNo)
            );
        }
    }
    public record SubjectSearchResultsAndErrors<T> (List<Tuple<Subject, T>> results, Map<Subject, Exception> errors) {}
}