Placeholder for Django 5.0 db_default support

[sparrowt]

This is currently a bit light on detail but I wanted to put in a ticket early so that this is tracked.

Since this ticket was fixed in May 2023 https://code.djangoproject.com/ticket/470#comment:69 there is now an option db_default coming in Django 5.0 https://docs.djangoproject.com/en/dev/releases/5.0/#database-computed-default-values

If the description in this open PR is still correct michiya/django-pyodbc-azure#38 then we may need to port those (or similar) changes to this repo, in order to drop the DEFAULT constraint so that removing a field with such a constraint does not fail.

[mShan0]

Thanks for the heads up!