fix bug: enums of underscored number

[sdghchj]

Describe the PR
support enums of underscored number

Relation issue
#1580

[codecov]

Codecov Report

Patch coverage: 100.00% and no project coverage change.

Comparison is base (5774b7b) 83.79% compared to head (97189ae) 83.80%.

❗ Current head 97189ae differs from pull request most recent head 9ff5016. Consider uploading reports for the commit 9ff5016 to get more accurate results

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #1581   +/-   ##
=======================================
  Coverage   83.79%   83.80%           
=======================================
  Files          19       19           
  Lines        3745     3747    +2     
=======================================
+ Hits         3138     3140    +2     
  Misses        520      520           
  Partials       87       87           

Impacted Files	Coverage Δ
package.go	73.33% <100.00%> (+0.51%)	⬆️

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[ubogdan]

Please take into consideration that @Nerzal is making efforts to finish v2 (OAS3 integration). These fixes sometimes create conflicts that are hard to manage via rebase.

[ubogdan]

Some unit tests are missing :)

[Nerzal]

I try to keep track of what needs to be merged & reimplemented into V2 branch, so no worries.