chore(refactor): improve code quality

[ubogdan]

Describe the PR
Reduce code complexity in gen/gen.go and cmd/swag/main.go
Remove testdata generated docs garbage

Relation issue
NONE

Additional context
NONE

[codecov-io]

Codecov Report

Merging #540 into master will increase coverage by 0.29%.
The diff coverage is 100%.

@@            Coverage Diff            @@
##           master    #540      +/-   ##
=========================================
+ Coverage    86.9%   87.2%   +0.29%     
=========================================
  Files           7       7              
  Lines        1550    1555       +5     
=========================================
+ Hits         1347    1356       +9     
+ Misses        119     117       -2     
+ Partials       84      82       -2

Impacted Files	Coverage Δ
gen/gen.go	96.69% <100%> (+7.03%)	⬆️
parser.go	81.93% <0%> (-0.46%)	⬇️

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