Improvement to honour the locale for email notifications.

[Thisara-Welmilla]

Issue:

• Email OTP locale doesn't work for federated users even with 'Assert identity using mapped local subject identifier' toggled on wso2/product-is#20606

Improvement to resolve locale attribute value of the authenticated user:
If a local user exists for the authenticated user, retrieve the locale value from the userStore. If no local user exists (either because it is the first time federated authentication or JIT provisioning is disabled), check the event properties for a local value, which will be set by the email authenticator step if there is a locale claim as an IDP claim. If neither of these conditions are met, set the default locale value.

[CLAassistant]

All committers have signed the CLA.

[jenkins-is-staging]

PR builder started
Link: https://github.com/wso2/product-is/actions/runs/9868033876

[jenkins-is-staging]

PR builder completed
Link: https://github.com/wso2/product-is/actions/runs/9868033876
Status: success

[jenkins-is-staging]

Approving the pull request based on the successful pr build https://github.com/wso2/product-is/actions/runs/9868033876

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 24 lines in your changes missing coverage. Please review.

Project coverage is 34.64%. Comparing base (79422ff) to head (2b85a5c).

Files with missing lines	Patch %	Lines
...nt/handler/notification/util/NotificationUtil.java	0.00%	23 Missing ⚠️
...ndler/notification/DefaultNotificationHandler.java	0.00%	1 Missing ⚠️

❌ Your patch check has failed because the patch coverage (0.00%) 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     #249      +/-   ##
============================================
- Coverage     34.82%   34.64%   -0.19%     
  Complexity      515      515              
============================================
  Files            74       74              
  Lines          4945     4942       -3     
  Branches        640      637       -3     
============================================
- Hits           1722     1712      -10     
- Misses         3058     3072      +14     
+ Partials        165      158       -7     

Flag	Coverage Δ
unit	20.47% <0.00%> (+0.01%)	⬆️

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