Description (*)

Fixes #36660
Adds public property support to DataObjectProcessor output serialization and snake_case constructor hydration in ServiceInputProcessor, enabling promoted/readonly DTOs for message queue payloads. Includes unit/integration tests and docs for getter vs public property precedence.

Example DTO:

class QueueMessage
{
    public function __construct(
        public readonly int $salesOrderId
    ) {}
}

Fixed Issues (if relevant)

1. Fixes magento/magento2#36660

Manual testing scenarios (*)

1. Run unit tests:
   • ServiceInputProcessorTest.php
   • DataObjectProcessorTest.php
2. Run integration test:
   • MessageEncoderTest.php
3. Publish/consume a message using an object_interface topic with a DTO using readonly promoted properties and verify JSON payload includes the property and consumer receives hydrated values.

Questions or comments

Contribution checklist (*)

• Pull request has a meaningful description of its purpose
• All commits are accompanied by meaningful commit messages
• All new or changed code is covered with unit/integration tests (if applicable)
• README.md files for modified modules are updated and included in the pull request if any README.md predefined sections require an update
• All automated tests passed successfully (all builds are green)