Support typechecking through_defaults for ManyToManyField

[danlamanna]

From the relevant django documentation section:

beatles.members.add(john, through_defaults={"date_joined": date(1960, 8, 1)})

It would be nice if django-autotyping could verify that date_joined belongs on the Membership model and that the value is the correct type.

[Viicos]

Thanks for the feature request, I'll try to see if it's possible to work on it next week.