Add API Chat and Marketplace Assistant feature implementations

[ashera96]

Purpose

Syncing AI feature implementation available under the feature branch with the master branch.

Related PRs:

• Add devportal rest api changes for API Chat feature #12347
• Marketplace assistant #12355
• Fix error flow error message propagate issue #12358
• Fix test failures and address review comments #12359

[codecov]

Codecov Report

Attention: Patch coverage is 6.83572% with 845 lines in your changes are missing coverage. Please review.

Project coverage is 41.93%. Comparing base (e94b4fd) to head (6984829).
Report is 3 commits behind head on master.

❗ Current head 6984829 differs from pull request most recent head 9bc1f11. Consider uploading reports for the commit 9bc1f11 to get more accurate results

Files	Patch %	Lines
...ava/org/wso2/carbon/apimgt/impl/utils/APIUtil.java	0.00%	88 Missing ⚠️
...fier/MarketplaceAssistantApiPublisherNotifier.java	0.00%	69 Missing ⚠️
...imgt/rest/api/store/v1/dto/ApiChatResponseDTO.java	0.00%	67 Missing ⚠️
...mgt/rest/api/store/v1/impl/ApisApiServiceImpl.java	0.00%	66 Missing ⚠️
...re/v1/impl/MarketplaceAssistantApiServiceImpl.java	3.70%	52 Missing ⚠️
...pimgt/rest/api/store/v1/dto/ApiChatRequestDTO.java	0.00%	46 Missing ⚠️
...st/api/store/v1/dto/ApiChatRequestResponseDTO.java	0.00%	46 Missing ⚠️
...t/api/store/v1/dto/ApiChatResponseResourceDTO.java	0.00%	38 Missing ⚠️
...t/api/store/v1/dto/MarketplaceAssistantApiDTO.java	0.00%	38 Missing ⚠️
...est/api/store/v1/dto/ApiChatRequestApiSpecDTO.java	0.00%	30 Missing ⚠️
... and 20 more

Additional details and impacted files

@@             Coverage Diff              @@
##             master   #12357      +/-   ##
============================================
- Coverage     47.62%   41.93%   -5.69%     
- Complexity     4192    15691   +11499     
============================================
  Files          1840     1849       +9     
  Lines        136532   136841     +309     
  Branches      19767    19823      +56     
============================================
- Hits          65019    57386    -7633     
- Misses        63857    72232    +8375     
+ Partials       7656     7223     -433     

Flag	Coverage Δ
integration_tests	41.93% <6.83%> (-0.49%)	⬇️
unit_tests	?

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