test: Update test coverage for tenant domain validation changes

[ramonschriks]

Changes

Added test coverage for previous added issuer claim validation with custom domain.

• Added expecting failure scenario with invalid domain not matching token issuer
• Added expecting failure scenario with invalid domain AND invalid custom domain not matching token issuer
• Added scenario with custom domain matching token issuer, should validate.
• Added scenario with custom domain not matching token issuer, should validate with tenant domain

References

Ref: #755

Contributor Checklist

• I agree to adhere to the Auth0 General Contribution Guidelines.
• I agree to uphold the Auth0 Code of Conduct.

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (2dd8a74) 99.97% compared to head (f32478b) 100.00%.
Report is 1 commits behind head on main.

Additional details and impacted files

@@              Coverage Diff              @@
##               main      #756      +/-   ##
=============================================
+ Coverage     99.97%   100.00%   +0.02%     
  Complexity     1383      1383              
=============================================
  Files            62        62              
  Lines          4781      4781              
=============================================
+ Hits           4780      4781       +1     
+ Misses            1         0       -1     

Flag	Coverage Δ
unittestsvalidate	100.00% <100.00%> (+0.02%)	⬆️

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[evansims]

LGTM; thanks @ramonschriks!