Token issuer cache improvement

[mpmadhavig]

$subject

This fix will,

• Stop adding the same token to the cache, which leading to cache invalidation due to cache renewal.
• Adds the entries to the cache, retrieved from the DB during a cache miss.

Test fix:

• For invalid JWTs, the token retrieval should fail -> hence changed the test data to cater this

Resolves wso2/product-is#23149

[codecov]

Codecov Report

Attention: Patch coverage is 14.28571% with 18 lines in your changes missing coverage. Please review.

Project coverage is 56.91%. Comparing base (28a1b03) to head (b6e9c0f).

Files with missing lines	Patch %	Lines
...arbon/identity/oauth2/token/AccessTokenIssuer.java	0.00%	15 Missing ⚠️
.../identity/oauth/cache/AuthorizationGrantCache.java	50.00%	2 Missing and 1 partial ⚠️

❌ Your patch check has failed because the patch coverage (14.28%) is below the target coverage (80.00%). You can increase the patch coverage or adjust the target coverage.

Additional details and impacted files

@@             Coverage Diff              @@
##             master    #2734      +/-   ##
============================================
- Coverage     56.92%   56.91%   -0.02%     
+ Complexity     8576     8565      -11     
============================================
  Files           654      654              
  Lines         48424    48436      +12     
  Branches      10252    10257       +5     
============================================
- Hits          27567    27565       -2     
- Misses        16957    16970      +13     
- Partials       3900     3901       +1     

Flag	Coverage Δ
unit	39.97% <14.28%> (-0.01%)	⬇️

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[jenkins-is-staging]

PR builder started
Link: https://github.com/wso2/product-is/actions/runs/13564819603

[jenkins-is-staging]

PR builder completed
Link: https://github.com/wso2/product-is/actions/runs/13564819603
Status: success

[jenkins-is-staging]

Approving the pull request based on the successful pr build https://github.com/wso2/product-is/actions/runs/13564819603