Relax code coverage settings

[kelle]

add code coverage settings in the pyproject.toml and adopt relaxed settings.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 71.32%. Comparing base (0e08069) to head (dd13ece).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #225      +/-   ##
==========================================
- Coverage   71.48%   71.32%   -0.16%     
==========================================
  Files          19       19              
  Lines        1655     1653       -2     
  Branches      211      210       -1     
==========================================
- Hits         1183     1179       -4     
- Misses        384      387       +3     
+ Partials       88       87       -1     

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