Add hooks to update Allauth email for a user from the Django contrib.auth panel without altering the contrib.auth.models.User model in any way

manage.py

""" App administration """
from django import forms
from django.contrib import admin
from django.contrib.auth.admin import UserAdmin as BaseUserAdmin
from django.contrib.auth.models import User
from django.contrib.auth.forms import UserCreationForm, UserChangeForm
from django.contrib.auth.decorators import login_required
from django.utils.translation import gettext_lazy as _

from allauth.account.models import EmailAddress
from myapp.models.user import Profile
from myapp.forms import ProfileForm

# Require Allauth login:
# https://django-allauth.readthedocs.io/en/latest/advanced.html#admin
admin.site.login = login_required(admin.site.login)

class AllEmailField(forms.EmailField):
    """ Extend email validation to check Allauth tables as well """

    def validate(self, value):
        super().validate(value)
        exists = EmailAddress.objects.filter(email=value).count()
        if exists > 0:
            raise forms.ValidationError(_("E-mail address is already in use"), 'invalid')


class CustomUserCreationForm(UserCreationForm):
    """ User Creation with additional model fields """
    # add fields which are not part of Django default admin
    # Custom email validator validates email uniqueness, also with allauth table
    email = AllEmailField(widget=forms.EmailInput(), required=False)
    first_name = forms.CharField(required=False)
    last_name = forms.CharField(required=False)

    class Meta(UserCreationForm):
        model = User
        fields = '__all__'

class CustomUserChangeForm(UserChangeForm):
    """ User Edit with additional model fields """
    # Custom email validator validates email uniqueness, also with allauth table
    email = AllEmailField(widget=forms.EmailInput(), required=False)
 
    class Meta(UserCreationForm):
        model = User
        fields = '__all__'
 


# Define an inline admin descriptor for Profile model
# which acts a bit like a singleton
class ProfileInline(admin.StackedInline):
    """ User Profile form """
    model = Profile
    form = ProfileAdminForm
    can_delete = False

class UserAdmin(BaseUserAdmin):
    """ Extend User Admin """
    # Override user creation form
    # add fields which are not part of Django default admin
    add_form = CustomUserCreationForm
    add_fieldsets = BaseUserAdmin.add_fieldsets + (
        (None, {'fields': ('email', 'first_name', 'last_name')}),
    )
    # override Edit / change form
    form = CustomUserChangeForm

    # Add profile inline
    inlines = (ProfileInline, )
    list_per_page = 20

    def save_model(self, request, obj, form, change):
        # Keep email address updated with Allauth
        # only if email field has changed:
        if not 'email' in form.changed_data:
            # go ahead with original save action
            super().save_model(request, obj, form, change)
        else:
            # first: check if email already exists in Django Allauth
            exists = EmailAddress.objects.filter(email=obj.email).count() > 0
            # Is it one of our own addresses?
            is_own = obj.pk and EmailAddress.objects.filter(user=obj, email=obj.email).count() > 0

            if exists:
                if is_own:
                    # go ahead and make this our primary email address
                    super().save_model(request, obj, form, change)
                    email = EmailAddress.objects.filter(user=obj, email=obj.email).get()
                    email.primary = True
                    email.save()
                    return
                else:
                    # this should already have been handled by validation in CustomUserChangeForm
                    raise forms.ValidationError(_("E-mail address is already in use by another account"), 'invalid')

            # If we have an existing user object
            if obj.pk:
                # obj has the changed email address
                # so get original value from DB, if it exists
                orig_email = User.objects.get(pk=obj.pk).email
                try:
                    # only if email was set previously (orig_email)
                    exists = EmailAddress.objects.filter(user=obj, email=orig_email).get()
                    # update existing email address from user
                    exists.primary = True
                    exists.change(request, obj.email, confirm=False)
                except EmailAddress.DoesNotExist:
                    # we should create a new Email Address after the User has been saved
                    exists = False
            else:
                exists = False

            super().save_model(request, obj, form, change)

            # email was not set before in Allauth
            # add it as primary email to allauth table
            if not exists:
                email = EmailAddress.objects.create(user=obj, email=obj.email, primary=True)


# Re-register UserAdmin
admin.site.unregister(User)
admin.site.register(User, UserAdmin)