Improve client error handling for notification template API

[madurangasiriwardena]

Resolves wso2/product-is#22593
Depends on wso2/identity-api-server#833

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 13 lines in your changes missing coverage. Please review.

Project coverage is 34.85%. Comparing base (79422ff) to head (9ee7a23).
Report is 7 commits behind head on master.

Files with missing lines	Patch %	Lines
...bon/email/mgt/NotificationTemplateManagerImpl.java	0.00%	12 Missing ⚠️
...so2/carbon/email/mgt/EmailTemplateManagerImpl.java	0.00%	1 Missing ⚠️

❌ Your patch status 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     #304      +/-   ##
============================================
+ Coverage     34.82%   34.85%   +0.03%     
  Complexity      515      515              
============================================
  Files            74       74              
  Lines          4945     4940       -5     
  Branches        640      638       -2     
============================================
  Hits           1722     1722              
+ Misses         3058     3053       -5     
  Partials        165      165              

Flag	Coverage Δ
unit	20.48% <0.00%> (+0.03%)	⬆️

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