Apply IDE refactoring suggestions

[martincostello]

Cherry-pick code refactoring/modernisation from #3252.

[codecov-commenter]

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Codecov Report

Attention: Patch coverage is 92.85714% with 1 line in your changes missing coverage. Please review.

Project coverage is 83.63%. Comparing base (bafd6d6) to head (fcfcdd6).
Report is 4 commits behind head on master.

Files with missing lines	Patch %	Lines
...ggerGen/SchemaGenerator/OpenApiSchemaExtensions.cs	50.00%	1 Missing ⚠️

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Additional details and impacted files

@@            Coverage Diff             @@
##           master    #3254      +/-   ##
==========================================
- Coverage   83.64%   83.63%   -0.01%     
==========================================
  Files          76       76              
  Lines        3185     3184       -1     
  Branches      540      540              
==========================================
- Hits         2664     2663       -1     
  Misses        521      521              

Flag	Coverage Δ
Linux	83.63% <92.85%> (-0.01%)	⬇️
Windows	83.63% <92.85%> (-0.01%)	⬇️
macOS	83.63% <92.85%> (-0.01%)	⬇️

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