[Feature]: Treat built-in LLM provider templates as read-only in Gateway

[Tharanidk]

Please select the area the issue is related to

Gateway

Please select the aspect the issue is related to

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

Suggested Feature

Built-in LLM provider templates should be treated as read-only. Users must not be able to update or delete them from any surface.

In the Platform API / control plane, PUT / PATCH / DELETE on a built-in template are blocked, as we treat them as read-only templates.But in the Gateway REST APIs, PUT / DELETE have no such guard, built-in templates can be updated or deleted. Also, when the gateway is restarted, those changes are lost during reseeding (deleted built-ins are re-created).
Since built-in templates are shipped and maintained by WSO2, modifying or deleting them should be restricted.

Proposed Solution

• Block update and delete operations on built-in templates. Requests must be rejected with a clear, actionable error message rather than failing silently or partially applying.

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.