Allow update of related modules in USER_ATTR_MAP

[gergelypolonkai]

By using the built-in User model of Django (django.contrib.auth.models) I can’t store a lot of fields, like phone number. However, if I set "settings.phone": "phone" in USER_ATTR_MAP, it won’t do anything (naturally, as the implementation calls setattr() on the user object.) Would it be possible to make it so it can update related models, too? Or is this already possible in a way I’m not aware of?