Any collection-alike object is a valid resource for us. Even arrays IIRC (in earlier versions, we converted them to `ArrayCollection`s in order to filter them).

While most of the use cases involve repositories, the idea that everything is doctrine-persistence backed is wrong IMO.

I could just build a service that produces selectable datasets and expose a `Selectable`. That's pretty much where the flexibility of the API lies imo.

Introducing this limiting plugin manager to avoid a couple of checks elsewhere is wrong imo.

In addition to that, you also limited it to a single ObjectManager here.