djadhere/adhesions/backends.py

from django.contrib.auth.models import User
from django.contrib.contenttypes.models import ContentType
from django.contrib.auth.backends import ModelBackend

from .models import Adherent


class AdherentBackend(ModelBackend):
    def authenticate(self, username, password=None, **kwargs):
        if str(username).lower().startswith("adt"):
            username = str(username)[3:]
        try:
            adherent_id = int(username)
        except ValueError:
            return None
        user_type = ContentType.objects.get_for_model(User)
        try:
            user = Adherent.objects.get(adherent_type=user_type, id=adherent_id).adherent
        except Adherent.DoesNotExist:
            UserModel().set_password(password) # https://code.djangoproject.com/ticket/20760
        else:
            if user.check_password(password) and self.user_can_authenticate(user):
                return user