set_alias support for nested attributes

[dacevedo12]

I have a use case where the parent resolver returns something like this:

Person(name="John", state=PersonState(married=False))

To implement person { married }, you would need to create a new resolver returning parent.state.married, and in a large schema, there are many of these trivial resolvers.

It would be great if set_alias supported nested attributes, so one could do person.set_alias("married", "state.married"), maybe using operator.attrgetter instead of getattr.