fix(JWT): Response with 401 on token payload validation

[provinzkraut]

Fix a bug introduced in #3692 that would cause a 500 status response to be returned when ValidationError was raised during the token payload conversion.

This was caused by the switch to msgspec for converting the token payload after decoding and verification, and the lack of error handling for this case.

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarCloud

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 98.28%. Comparing base (eb31341) to head (cb1e221).
Report is 2 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #3705   +/-   ##
=======================================
  Coverage   98.28%   98.28%           
=======================================
  Files         330      330           
  Lines       15035    15041    +6     
  Branches     2393     2394    +1     
=======================================
+ Hits        14777    14783    +6     
  Misses        116      116           
  Partials      142      142           

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[github-actions]

Documentation preview will be available shortly at https://litestar-org.github.io/litestar-docs-preview/3705