fix: Update codebase to use newer django syntax

[abhiabhi94]

• all commands of django_extensions now inherit from a base command _BaseDjangoExtensionsCommand.
• this helps in defining constant at a single place.(The _ is prefixed intentionally to indicate the class as an internal API.)
• handle django41 deprecation warnings.
• update some test code to use upgraded version of django code.

[abhiabhi94]

in newer version of django, this value should be list/tuple of Tags or __all__. You can check the documentation here.

For mypy linting to work well with backward comptability, I think one of the solution would be to do something of the form:

from typing import List, Tuple, Union

from django.core.checks import Tags

requires_system_checks: Union[bool, List[Tags], Tuple[Tags], str]

Instead of making this change everywhere in the codebase, I think it would be better to create some sort of BaseCommandand let all commands inherit from it.

Would it be acceptable? Any suggestions are welcome.

[abhiabhi94]

I have had to make some changes to workaround mypy which might make the diff a bit more than it should have.

As of now, it seems that mypy doesn't necessarily work well with inherited class attributes, hence had to ignore it at certain places as a workaround.

The issue can be demonstrated by the example below:

from typing import List

class A:
    a: List[int]

class B:
    a = []  # <- mypy tends to complain about this

I have created an issue there as well python/mypy#10375, but am yet to receive a response. So, for the time being, I think we can use the type: ignore thing as a workaround.

[camilonova]

Looks like a big change and the codebase has changed a lot since it was first proposed. I'm closing this. Thank you.