SNOW-1206259 Handle OKTA Auth invalid responses more gracefully

[sfc-gh-mhofman]

Description

Native OKTA SSO Authn improvements of error handling.

Checklist

• Code compiles correctly
• Code is formatted according to Coding Conventions
• Created tests which fail without the change (if possible)
• All tests passing (dotnet test)
• Extended the README / documentation, if necessary
• Provide JIRA issue id (if possible) or GitHub issue id in PR name

[codecov]

Codecov Report

Attention: Patch coverage is 88.88889% with 8 lines in your changes are missing coverage. Please review.

Project coverage is 84.17%. Comparing base (ee843a4) to head (c982f4b).
Report is 1 commits behind head on master.

Files	Patch %	Lines
...flake.Data/Core/Authenticator/OktaAuthenticator.cs	88.88%	5 Missing and 3 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #884      +/-   ##
==========================================
+ Coverage   84.11%   84.17%   +0.05%     
==========================================
  Files          88       88              
  Lines        9401     9392       -9     
  Branches      885      885              
==========================================
- Hits         7908     7906       -2     
+ Misses       1260     1254       -6     
+ Partials      233      232       -1     

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