[Feature]: Support OpenAPI Specification in REST APIs

Please select the area the issue is related to

Platform API

Please select the aspect the issue is related to

Aspect/API (API backends, definitions, contracts, interfaces, OpenAPI)

Suggested Feature

We currently support creating REST APIs from Platform API by providing individual REST resources etc, but it doesn't allow providing OpenAPI spec to them. Users should be able to upload OpenAPI specs to APIs, retrieve, update them. This is essential when we need to publish the API to the developer portal.

Related Issues

No response

Steps to Verify

• Design Document — A detailed design document has been created and reviewed, covering architecture, data flow, and edge cases.
• Design Mail — A design summary email has been sent to relevant stakeholders for awareness and feedback.
• Code Review — All code changes have been peer-reviewed and approved according to the project's review standards.
• Testing Complete — Adequate unit, integration, and/or end-to-end tests have been written and are passing.
• Documentation Review — User-facing and/or developer documentation has been updated to reflect the new feature and reviewed.
• Feature Complete — The feature is fully implemented, all checklist items above are done, and it is ready for release.

Start by reviewing the Platform API area and the existing REST resource creation flow, then clarify how OpenAPI specifications should be uploaded, retrieved, and updated. Define the design, API behavior, validation and edge cases, and verify completion with unit, integration, or end-to-end tests plus updated user and developer documentation.