Move signal import to django.core

[AlanCoding]

Description of the Change

Hi :wave: , I believe this is causing us a problem, but I lack technical rigor to be able to explain it fully. By applying this change under certain circumstances, I seem to avoid a core dump that happens as uWSGI recycles workers when it is running in the default prefork mode. The most relevant description of the series of events is this comment: https://github.com/unbit/uwsgi/issues/1969#issuecomment-462252471

Here, I just wish to present this as an improvement to follow best practice. In the django.test.signals module, you can see it imports from this modification with no modifications.

https://github.com/django/django/blob/main/django/test/signals.py

However, somewhat obviously... if you import this test module, you will also register all the test signal connections. Now, that shouldn't do anything because the setting_changed signal is documented to only fire when running tests. However, it also pulls in a lot of other imports which just aren't needed, and as this happens in settings, it triggers fairly early in app load order.

This argument also applies to 1 import in DRF, which I also hope to submit a patch for. I'm still working out final testing on my side, so consider this a draft as of opening.

Checklist

• [x] PR only contains one change (considered splitting up PR)
• [ ] unit-test added
• [ ] documentation updated
• [x] CHANGELOG.md updated (only for user relevant changes)
• [x] author name in AUTHORS

[AlanCoding]

For some more background - here is an issue where they requested to move this signal out of tests https://code.djangoproject.com/ticket/20349

And in 2014 it was implemented in https://github.com/django/django/commit/5dddd79433ceb88ab67d9851b49a44ce5b8f509c

Nonetheless it seems plausible that libraries still have the old import, and that it has even proliferated.

[AlanCoding]

It turns out that the change was already adopted into Django Rest Framework here https://github.com/encode/django-rest-framework/pull/8699

[dopry]

@AlanCoding this looks like a reasonable change. I don't think additional unit tests are needed here as long as tests continue passing. Can you update your branch to add a note to the CHANGELOG.md and add yourself to AUTHORS?

[codecov[bot]]

Codecov Report

Merging #1357 (aa37593) into master (a30001f) will not change coverage. The diff coverage is 100.00%.

@@           Coverage Diff           @@
##           master    #1357   +/-   ##
=======================================
  Coverage   97.54%   97.54%           
=======================================
  Files          32       32           
  Lines        2120     2120           
=======================================
  Hits         2068     2068           
  Misses         52       52           

Files	Coverage Δ
oauth2_provider/settings.py	100.00% <100.00%> (ø)

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