refactor: replace exception raising with error flag resolution

[gruebel]

This PR

• this has actually no consequences for SDK users, because we already properly sending the errors inside the flag evaluation and only internally raised an exception. if someone used the privately marked methods, then it is a breaking change for them, but that's nothing we guarantee stability for.

Related Issues

Fixes #466

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 97.44%. Comparing base (5a2825b) to head (ec2d44a).
Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #474      +/-   ##
==========================================
- Coverage   97.85%   97.44%   -0.42%     
==========================================
  Files          37       37              
  Lines        1723     1759      +36     
==========================================
+ Hits         1686     1714      +28     
- Misses         37       45       +8     

Flag	Coverage Δ
unittests	97.44% <100.00%> (-0.42%)	⬇️

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