Added unit test to validate JsonStringEnumConverter working as expected

[WhitWaldo]

Description

I prefer the JsonSerializer retaining the string over int values for enums, so when I saw the bug reported in #1160 , I though I'd go ahead and tackle it. While I was unable to reproduce the experienced issue, I went ahead and added a unit test to the suite to prove out that this experience both works as-is and doesn't break going forward.

Issue reference

Please reference the issue this PR will close: #1160

Checklist

Please make sure you've completed the relevant tasks for this PR, out of the following list:

* [ ] Code compiles correctly

• Created/updated tests
  * [ ] Extended the documentation

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (bb3f97a) 66.53% compared to head (1f483b9) 66.53%.

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #1174   +/-   ##
=======================================
  Coverage   66.53%   66.53%           
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  Files         171      171           
  Lines        5752     5752           
  Branches      626      626           
=======================================
  Hits         3827     3827           
  Misses       1776     1776           
  Partials      149      149           

Flag	Coverage Δ
net6	48.00% <ø> (-18.53%)	⬇️
net7	66.52% <ø> (ø)
net8	66.52% <ø> (ø)

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