Refactor the Join lookup on transfer user

[rachidatecs]

Issue description

Right now we use a brute force approach that defines which field on user and joined fields from other models need to be tackled when transferring a user. For a more solid approach, use Django's lookup to find and handle these fields.

The downside with the current approach is that the transfer setup up could break as we add in new models with joins to user and require more code maintenance.

Acceptance criteria

• [ ] the user transfer logic (originally made in #2579 now uses django lookups to gather all joined fields before completing the transfer.

Additional context

I (Rachid) tried using a related field lookup when working on #2579 which was partly successful. The lookup (based on Dave's work on the 'join' alert on contacts) works, but the field update fails:

`def post(self, request, user_id): current_user = get_object_or_404(User, pk=user_id) selected_user_id = request.POST.get('selected_user') selected_user = get_object_or_404(User, pk=selected_user_id)

    try:
        related_objects = []

        for related_field in selected_user._meta.get_fields():
            if related_field.is_relation and related_field.auto_created:
                related_manager = getattr(selected_user, related_field.get_accessor_name(), None)
                if related_manager:
                    if hasattr(related_manager, "get_queryset"):
                        queryset = related_manager.get_queryset()
                    else:
                        queryset = [related_manager]

                    for obj in queryset:
                        field_name = related_field.field.name

                        if related_field.many_to_one or related_field.one_to_one:
                            setattr(obj, field_name, current_user)
                        elif related_field.many_to_many:
                            print(f'many to many handling')
                            if selected_user in related_manager.all():
                                related_manager.remove(selected_user)
                            related_manager.add(current_user)

                        obj.save()

Links to other issues

No response

[vickyszuchin]

Added "refinement" label, no ACs defined. @rachidatecs would you add ACs to this ticket?

[abroddrick]

temporary slotting in 55

[abroddrick]

Added ACs and some other details, marking this as ready, due to the nature of this being a code maintenance issue, would like it to be done anywhere within the next 3 sprints.