How to store objects in related models in Django?

Question

Django

I need to register a user, but when he registers, an entry must first be created in another model (Project) and the user must be bound (ForeignKey) to this entry. I decided that in the form_valid method I would select the maximum id value from the Project, add one to it and then create the record I need in the Project + Bind User by project_id + 1

class Registration(FormView):

    template_name = 'profile/registration.html'
    form_class = RegistrationForm

    success_url = 'cabinet:main'

    def form_valid(self, form):
        self.object = form.save(commit=False)
        qs = models.Project.objects.all().aggregate(Max('id'))
        project_id = (qs['id__max']) + 1
        project = models.Project(
            id=project_id,
            project_name='Новый проект',
        )
        project.save()
        self.object.project = project_id #PrimaryKey
        self.object = form.save()

        messages.success(self.request, 'Вы успешно зарегестрированы')
        return super().form_valid(form)

As a result, it gives me an error:
Cannot assign "9": "Profile.project" must be a "Project" instance.
at the same time, an entry is created in model.Project, but the function does not see it.
How can this problem be solved?

Answer 1

It is necessary to transfer not PK, but an object instance.
self.object.project = project