exposes a way to provide default options from the controller.
call the method on the serializer, and not the object.

- this now allows using the method that’s defined (if one is) in the serializer.
this commit does several things.

- first, pass options to the serializer properly.
- second, allow specifying a serializer in the association.
- third, move the each_serializer to serializer after instantiating the array level serializer.

Note that the third fix is a breaking change but bring parity to what is possible in the controller.
pass options through to the serializer that the array serializer is instantiating.