Error with adapted_fields when subclassing attr class

• cattrs version: 1.8.0
• Python version: 3.8
• Operating System: PopOS

Description

The current implementation of adapted_fields check first if the type if a dataclass when you should instead test if it's a attr class first. This leads to miscategorizing type as non attr class and not use the attrs_fields

What I Did

    @strawberry.type  # definie method typical of python dataclass that gets picked up by cattr.is_dataclass
    @attr.define
    class UserAttributes:
        birthday: Optional[date] = attr.field(validator=attr.validators.optional(attr.validators.instance_of(date)),
                                              default=None)
    structure({}, UserAttributes)  # fails with KeyError 'birthday' because the default of attr is not handled

Start at the adapted_fields implementation and reproduce the issue with the UserAttributes example from the report. Check how the type is classified before attrs fields are read, then verify that structure({}, UserAttributes) handles the birthday default without a KeyError. Add or update a regression test for the subclassing and decorator combination described.