refactor: simplify code and improve tests

[alexander-akait]

This PR contains a:

• bugfix
• new feature
• code refactor
• test update
• documentation update
• typo fix
• metadata update

Motivation / Use-Case

simplify tests + more tests + refactor

Breaking Changes

No

Additional Info

No

[codecov]

Codecov Report

❌ Patch coverage is 85.71429% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 95.87%. Comparing base (5e986db) to head (7d45355).

Files with missing lines	Patch %	Lines
src/middleware.js	85.71%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #2159      +/-   ##
==========================================
+ Coverage   95.77%   95.87%   +0.10%     
==========================================
  Files          13       13              
  Lines         899      898       -1     
  Branches      270      269       -1     
==========================================
  Hits          861      861              
+ Misses         38       37       -1     

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