Feature/strict flag post signing

[MatthiasValvekens]

Description of the changes

Successor PR to #476 to address #466.

Checklist

Please go over this checklist to increase the chances of your PR being worked on in a timely manner. Deviations are allowed with proper justification (see previous section).

• I have read the project's CoC and contribution guidelines.
• [X} I understand and agree to the terms in the Developer Certificate of Origin as applied to this contribution.
• All new code in this PR has full test coverage.

For bug fixes (delete if not applicable)

• My changes do not affect any public API or CLI semantics.
• My PR adds regression tests (i.e. tests that fail if the bug fix is not applied).
• All new code in this PR has full test coverage.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 98.89%. Comparing base (4deaf2a) to head (72706a0).
Report is 3 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master     #487   +/-   ##
=======================================
  Coverage   98.89%   98.89%           
=======================================
  Files         116      116           
  Lines       16905    16913    +8     
=======================================
+ Hits        16718    16726    +8     
  Misses        187      187           

Flag	Coverage Δ
unittests	98.89% <100.00%> (+<0.01%)	⬆️

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