Add URLPattern options to django.url.conf since they were missing.

[LanDinh]

I have made things!

It's possible to pass in List[URLPattern] as argument to django.urls.include, which then results in List[URLPattern] as output of that function. The current type hints for all of django.urls.include, django.urls.path and django.urls.re_path don't support this use case - this PR adjust their type hints to support it.

Related issues

Fixes #582

[LanDinh]

Some follow-up work might be necessary on URLResolver, specifically the urlconf_name field - despite its name, it can also receive List[URLResolver] and List[URLPattern] as input (just look at the comments of the constructor in the Django implementation!), but I'm not sure what the exact full type / options are and don't want to mess up stuff, so I've left it out of this PR.

I took a quick look at the tests; it's not quite straightforward (I've never written any type checking test before). Is there some documentation somewhere that I could refer to on how to specify the expected output of cases? E. g. tests to make sure that List[URLPattern] will be expected and not raise a type error.

[sobolevn]

Yes,

• https://github.com/typeddjango/pytest-mypy-plugins
• error: https://github.com/typeddjango/pytest-mypy-plugins/blob/master/pytest_mypy_plugins/tests/test-simple-cases.yml#L52-L55

[sobolevn]

Awesome, thank you!

Can we please test that now it works?

[LanDinh]

I've tested it with my local snippet, it works :) Am now looking into writing a test for that.

[LanDinh]

Test added.

[sobolevn]

Thanks!