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/Security.java
IndexNameExpressionResolver expressionResolver
    ) throws Exception {
        logger.info("Security is {}", enabled ? "enabled" : "disabled");
        if (enabled == false) {
            return Collections.singletonList(new SecurityUsageServices(null, null, null, null));
        }
        systemIndices.init(client, clusterService);
        scriptServiceReference.set(scriptService);
        
        
        final List<BootstrapCheck> checks = new ArrayList<>();
        checks.addAll(
            Arrays.asList(
                new TokenSSLBootstrapCheck(),
                new PkiRealmBootstrapCheck(getSslService()),
                new SecurityImplicitBehaviorBootstrapCheck(nodeMetadata),
                new TransportTLSBootstrapCheck()
            )
        );
        checks.addAll(InternalRealms.getBootstrapChecks(settings, environment));
        this.bootstrapChecks.set(Collections.unmodifiableList(checks));
        threadContext.set(threadPool.getThreadContext());
        List<Object> components = new ArrayList<>();
        securityContext.set(new SecurityContext(settings, threadPool.getThreadContext()));
        components.add(securityContext.get());
        final RestrictedIndices restrictedIndices = new RestrictedIndices(expressionResolver);
        
        final List<AuditTrail> auditTrails = XPackSettings.AUDIT_ENABLED.get(settings)
            ? Collections.singletonList(new LoggingAuditTrail(settings, clusterService, threadPool))
            : Collections.emptyList();