refactor: assertion parsing

[eddycharly]

Explanation

Refactor assertion parsing.

[codecov]

Codecov Report

Attention: Patch coverage is 18.27957% with 76 lines in your changes missing coverage. Please review.

Project coverage is 21.05%. Comparing base (574b26e) to head (0104a37).
Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
pkg/core/assertion/assertion.go	18.27%	70 Missing and 6 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #514      +/-   ##
==========================================
+ Coverage   21.02%   21.05%   +0.03%     
==========================================
  Files          92       92              
  Lines        4300     4274      -26     
==========================================
- Hits          904      900       -4     
+ Misses       3324     3302      -22     
  Partials       72       72              

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