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
}, listener::onFailure));
    }
    
    void maybeIncrementDifferentiatorAndCreateNewProfile(Subject subject, ProfileDocument profileDocument, ActionListener<Profile> listener)
        throws IOException {
        final String uid = profileDocument.uid();
        final int index = uid.lastIndexOf("_");
        if (index == -1) {
            listener.onFailure(new ElasticsearchException("profile uid [{}] does not contain any underscore character", uid));
            return;
        }
        final String baseUid = uid.substring(0, index);
        final String differentiatorString = uid.substring(index + 1);
        if (differentiatorString.isBlank()) {
            listener.onFailure(new ElasticsearchException("profile uid [{}] does not contain a differentiator", uid));
            return;
        }
        final DomainConfig domainConfig = getDomainConfigForSubject(subject);
        
        if (domainConfig != null && domainConfig.suffix() != null) {
            assert differentiatorString.equals(domainConfig.suffix());
            listener.onFailure(
                new ElasticsearchException(
                    "cannot create new profile for ["
                        + subject.getUser().principal()
                        + "]."
                        + " A profile with uid ["
                        + profileDocument.uid()
                        + "] already exists and suffix setting of domain ["
                        + domainConfig.name()