Dynamic type

Use string as type to refer type that not defined yet.

when resolver called as_field or as_type, related type will be registered in resolver.typedef.REGISTRY, type can be registered at anytime before schema init.

when same name registered multiple time, registry will only keep latest type.

class FirstPet(resolver.Resolver):
    schema = 'Pet!'

    def resolve(self, **kwargs):
        return {
            'name': 'pet1',
            'age': 1
        }

class Pet(resolver.Resolver):
    schema = {
        'name': models.Pet._meta.get_field('name'),
        'age': models.Pet._meta.get_field('age'),
    }
Pet.as_type('Pet')

class Query(graphene.ObjectType):
    first_pet = FirstPet.as_field()