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
assertThat(featureSet.available(), is(true));
    }
    public void testEnabled() {
        SecurityInfoTransportAction featureSet = new SecurityInfoTransportAction(
            mock(TransportService.class),
            mock(ActionFilters.class),
            settings
        );
        assertThat(featureSet.enabled(), is(true));
        Settings disabled = Settings.builder().put(XPackSettings.SECURITY_ENABLED.getKey(), false).build();
        featureSet = new SecurityInfoTransportAction(mock(TransportService.class), mock(ActionFilters.class), disabled);
        assertThat(featureSet.enabled(), is(false));
    }
    @SuppressWarnings("rawtypes")
    public void testUsage() throws Exception {
        final boolean explicitlyDisabled = randomBoolean();
        final boolean enabled = explicitlyDisabled == false;
        final boolean operatorPrivilegesAvailable = randomBoolean();
        when(licenseState.isAllowed(Security.OPERATOR_PRIVILEGES_FEATURE)).thenReturn(operatorPrivilegesAvailable);
        Settings.Builder settings = Settings.builder().put(this.settings);
        if (explicitlyDisabled) {
            settings.put("xpack.security.enabled", "false");
        }
        final boolean httpSSLEnabled = randomBoolean();
        settings.put("xpack.security.http.ssl.enabled", httpSSLEnabled);
        final boolean transportSSLEnabled = randomBoolean();
        settings.put("xpack.security.transport.ssl.enabled", transportSSLEnabled);
        boolean configureEnabledFlagForTokenService = randomBoolean();
        final boolean tokenServiceEnabled;
        if (configureEnabledFlagForTokenService) {