如何为用户模型覆盖“ save_model”方法ModelAdmin？

Question

我尝试更改在Django admin中保存数据的逻辑。 我覆盖了save_model，但收到错误"<User: test_user>" needs to have a value for field "id" before this many-to-many relationship can be used.

class UserAdminForm(forms.ModelForm):
    middle_name = forms.CharField(label='Middle name')

    class Meta:
        labels = {
            'last_name': 'Last name',
            'first_name': 'First name',
            'password': 'Password',
        }

class UserAdmin(admin.ModelAdmin):
    form = UserAdminForm
    fields = ['username', 'password', 'last_name', 'first_name', 'middle_name', 'groups']
    list_display = ['username', 'last_name', 'first_name', ]

    def save_model(self, request, obj, form, change):
        print(form)