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/profile/ProfileServiceTests.java
results,
            errors.entrySet().stream().collect(Collectors.toUnmodifiableMap(entry -> "profile_" + entry.getKey(), Map.Entry::getValue))
        );
    }
    public static String getSampleProfileDocumentSource(String uid, String username, List<String> roles, long lastSynchronized) {
        return SAMPLE_PROFILE_DOCUMENT_TEMPLATE.formatted(
            uid,
            username,
            roles.stream().map(v -> "\"" + v + "\"").collect(Collectors.toList()),
            lastSynchronized
        );
    }
    private ProfileDocument randomProfileDocument(String uid) {
        return new ProfileDocument(
            uid,
            true,
            randomNonNegativeLong(),
            new ProfileDocumentUser(
                randomAlphaOfLengthBetween(5, 8),
                randomList(3, () -> randomAlphaOfLengthBetween(5, 8)),
                AuthenticationTestHelper.randomRealmRef(),
                "foo@example.com",
                randomAlphaOfLengthBetween(10, 20)
            ),
            Map.of(),
            null
        );
    }
}