[1.2.X] Fix the issue with generating http service using OpenAPI spec

[LakshanWeerasinghe]

Purpose

$subject

Fixes wso2/product-ballerina-integrator#1146

Screen.Recording.2025-09-04.at.15.27.01.mov

[Copilot]

Pull Request Overview

This PR fixes an issue with generating HTTP services using OpenAPI specifications. The fix ensures the design approach is properly populated before determining whether to use OpenAPI-based or regular service generation.

• Adds call to populateDesignApproach() to properly initialize service configuration
• Includes test resources and test case for OpenAPI spec-based service generation
• Adds validation to verify the fix works correctly with OpenAPI specifications

Reviewed Changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 1 comment.

File	Description
openapi.yaml	Test OpenAPI specification with albums API endpoints and schema definitions
add_http_service_from_openapi_spec.json	Test configuration for validating OpenAPI-based service generation
AddServiceTest.java	Adds test method and skips list for OpenAPI spec validation
HttpServiceBuilder.java	Core fix - adds populateDesignApproach() call before OpenAPI processing

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