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
);
            }
            return domainConfig;
        } else {
            return null;
        }
    }
    
    void updateProfileForActivate(Subject subject, VersionedDocument currentVersionedDocumentBySearch, ActionListener<Profile> listener)
        throws IOException {
        final ProfileDocument newProfileDocument = updateWithSubject(currentVersionedDocumentBySearch.doc, subject);
        if (shouldSkipUpdateForActivate(currentVersionedDocumentBySearch.doc, newProfileDocument)) {
            logger.debug(
                "skip user profile activate update because last_synchronized [{}] is within grace period",
                currentVersionedDocumentBySearch.doc.lastSynchronized()
            );
            listener.onResponse(currentVersionedDocumentBySearch.toProfile(Set.of()));
            return;
        }
        doUpdate(
            buildUpdateRequest(
                newProfileDocument.uid(),
                wrapProfileDocumentWithoutApplicationData(newProfileDocument),
                RefreshPolicy.WAIT_UNTIL
            ),
            ActionListener.wrap(updateResponse -> {
                listener.onResponse(
                    new VersionedDocument(newProfileDocument, updateResponse.getPrimaryTerm(), updateResponse.getSeqNo()).toProfile(
                        Set.of()
                    )