Replace hardcoded OpenAPI definition placeholder with actual API definition in DevPortal publish flow

Problem

In the DevPortal publishing flow, the code currently uses a hardcoded OpenAPI JSON template with only basic metadata (title, version, description) instead of the actual API definition.

File: platform-api/src/internal/service/devportal_service.go
Lines: 537-545
Method: publishAPIToDevPortalInternal

The current implementation creates a minimal OpenAPI spec placeholder:

apiDefinitionBytes := []byte(fmt.Sprintf(`{
    "openapi": "3.0.0",
    "info": {
        "title": "%s",
        "version": "%s",
        "description": "%s"
    },
    "paths": {}
}`, api.Name, api.Version, api.Description))

This doesn't reflect the actual API specification and should be replaced with the real API definition.

Expected Behavior

The code should retrieve and use the actual OpenAPI definition from the API object or repository.

Related

• PR: #136
• Comment: https://github.com/wso2/api-platform/pull/136#discussion_r2514972951
• Requested by: @DakshithaS