pep639: setuptools license and license-files fields

[bjlittle]

🚀 Pull Request

Description

This pull-request complies with PEP639 for setuptools, also see license and license-files.

Additionally avoids the following setuptools deprecation warning:

!!
          ********************************************************************************
          Please consider removing the following classifiers in favor of a SPDX license expression:
          License :: OSI Approved :: BSD License
          See https://packaging.python.org/en/latest/guides/writing-pyproject-toml/#license for details.
          ********************************************************************************
!!

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 89.80%. Comparing base (90e36fe) to head (256c114).
⚠️ Report is 101 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #6428   +/-   ##
=======================================
  Coverage   89.80%   89.80%           
=======================================
  Files          90       90           
  Lines       23752    23752           
  Branches     4418     4418           
=======================================
  Hits        21331    21331           
  Misses       1672     1672           
  Partials      749      749           

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[trexfeathers]

Thanks for your thorough research @bjlittle!