EZP-24834 adds concept of UserReference, which avoids the current user to be completely loaded at each request when the user is anonymous.

However, when authenticated (aka not anonymous), current user is still loaded and serialized with the token in the session. To increase performance and decrease session size, it is needed to take advantage of the new UserReference instead of the whole user object to get rid of the serialization of api user object in sessions, reducing network traffic needed when on memcached / redis for instance.