Re: I get a 404 error with “id-” in slug, I don't know if it's a bug or I'm doing something wrong.
I think you've found the wrong mailing list for this post. This mailing list is for discussing the development of Django itself, not for support using Django. This means the discussions of bugs and features in Django itself, rather than in your code using it. People on this list are unlikely to answer your support query with their limited time and energy.
For support, please follow the "Getting Help" page: https://docs.djangoproject.com/en/3.0/faq/help/ . This will help you find people who are willing to support you, and to ask your question in a way that makes it easy for them to answer.