Update supported versions, remove eol dj22 and py37, add dj5 and py12

[adamchainz]

Description of the Change

Drop EOL Python 3.7 and Django 2.2.

Add Python 3.12 and Django 5.0.

I looked back at #1264 to figure out the changes required.

Checklist

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

[codecov[bot]]

Codecov Report

Merging #1350 (2c701a0) into master (f580e2e) will decrease coverage by 0.01%. The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #1350      +/-   ##
==========================================
- Coverage   97.55%   97.54%   -0.01%     
==========================================
  Files          32       32              
  Lines        2123     2120       -3     
==========================================
- Hits         2071     2068       -3     
  Misses         52       52              

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

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[adamchainz]

The reduction in coverage percentage is only due to the removal of the lines in __init__.py.

[adamchainz]

🙌 Thanks for the updates and merges.