Fix django-stubs-ext missing breaking a production setup

[richardebeling]

As django-stubs-ext is required so that from django_stubs_ext import StrOrPromise doesn't fail on production, but I also don't want to duplicate the dependency version number across two files.

Opinions? Is there a better way? Maybe by specifying dependencies in pyproject.toml or something?

[janno42]

fine for me

[niklasmohrin]

Couldn't we just do

from typing import TYPE_CHECKING, Any

if TYPE_CHECKING:
    from django_stubs_ext import StrOrPromise
else:
    StrOrPromise = Any