fix: use sender for m2m signal dispatch connection

[cdubz]

This fix adds support for a use case where a single m2m through model is used on multiple models. When the receiver is used for the dispatch uid in this use case it cause duplicated logs because the through model signal connection happens multiple times.

By changing the m2m signal connection to use the sender for the dispatch uid this duplication is prevented because the signal connection only happens once for the through model.

Fixes #685

I wasn't able to run tests as I don't have a postgres database connection handy and I couldn't get the tests to work with SQLite. Test still need to be run and probably a test should be added for this use case.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 95.49%. Comparing base (5289482) to head (b8a36e3).
Report is 29 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #686      +/-   ##
==========================================
+ Coverage   95.21%   95.49%   +0.27%     
==========================================
  Files          31       32       +1     
  Lines        1025     1087      +62     
==========================================
+ Hits          976     1038      +62     
  Misses         49       49              

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[hramezani]

Thanks @cdubz for reporting the issue and for the fix PR.

You can easily run a Postgres in your machine by docker run --name some-postgres -e POSTGRES_PASSWORD=postgres -p 5432:5432 -d postgres and then you can add a test.

Please remember to add a changelog entry as well

[cdubz]

Oh yeah! I will add a test and changelog entry. Thanks!

[cdubz]

Ok, I think this is ready for review again -- not used to this set of formatting tools 😁

I confirmed the test I added reproduces the issue on master (and fails).

[hramezani]

Thanks @cdubz

[cdubz]

Thanks for the quick review!