Implement security suggestions from code scanning

[dalager]

• Pin Poetry version
• Use poetry packaged flake8 version for linting instead of installing with pip
• update SECURITY.md for vulnerability reporting
• updating packages

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 84.85%. Comparing base (901f3f0) to head (b1d8e5b).
Report is 5 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main      #27   +/-   ##
=======================================
  Coverage   84.85%   84.85%           
=======================================
  Files           7        7           
  Lines         284      284           
=======================================
  Hits          241      241           
  Misses         43       43           

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