How to properly organize the work of "non-entities" in the API code?

Question

API

That is, if we take the example of a forum or a social network, then if, for example, there is a User controller and a User Model, and for example, a communication room also has a controller and a model, then such a moment as news (let's say about users and groups) will not have a full-fledged models, and it should work with the User and Group models, what is the best way to deal with the news then?