How to make a table field able to store one unique value (True) and many others (False)?

Question

Django

Hello!
Prompt ways to implement the following logic:
I have a table, rules. Each entry is a separate set of rules, among which there is an activity flag field. If True, the rules are active, if False, respectively, no
Rules are specified in django-admin. And I understand that I can crutch this situation in other places. but I want it at the level of the model. Challenge: Only One set of rules can be active at a time. In other words, if the field value is True, it must be unique, if the value is False, uniqueness is not checked
How to implement this in Django

Answer 1

https://docs.djangoproject.com/en/3.2/ref/validators/