Django 4.2 preparation

[rtpg]

This makes some changes that get rid of deprecation warnings. Thanks to #862 for some initial exploratory work on this topic.

This removes Python 3.7 support as well as Django 3.2 support. The work here also preps for Django 5.0 properly speaking, but we won't label it as such until 5.0 is official

[codecov]

Codecov Report

Merging #869 (60064a7) into master (16db42e) will decrease coverage by 1.99%.
Report is 1 commits behind head on master.
The diff coverage is 50.00%.

@@            Coverage Diff             @@
##           master     #869      +/-   ##
==========================================
- Coverage   93.48%   91.49%   -1.99%     
==========================================
  Files           9        9              
  Lines         737      741       +4     
  Branches      132      133       +1     
==========================================
- Hits          689      678      -11     
- Misses         31       41      +10     
- Partials       17       22       +5     

Files Changed	Coverage Δ
taggit/managers.py	92.34% <33.33%> (-3.92%)	⬇️
taggit/models.py	98.29% <100.00%> (ø)

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