[Feature Request] Automatic REST API: Support for Nested Resource Endpoints (Hierarchical Routing)

[lsmith77]

Description

Is your feature request related to a problem? Please describe.
Currently, ZenStack's automatic REST API generates "flat" endpoints for all models (e.g., /thread/1 and /comment/2). While functional, this doesn't reflect the logical ownership and hierarchy of data. For resources that are strictly dependent on a parent—such as a Comment that must always belong to a Thread—a flat structure lacks semantic clarity and forces the client to manually manage foreign keys in every request.

Without nested routing, the API doesn't express the constraint that a child resource's lifecycle is bound to its parent.

Describe the solution you'd like
I would like the ability to configure hierarchical or "nested" endpoints within the automatic REST API. This would allow for URLs like:
GET /threads/:threadId/comments/:commentId

Key Requirements:

• Logical Scoping: Accessing a child via a nested route should automatically apply a filter to ensure the child actually belongs to the specified parent.
• Simplified Creation: A POST to /threads/1/comments should automatically associate the new comment with threadId: 1 without requiring the ID in the request body.
• ZModel Configuration: Ideally, this could be defined in the .zmodel file using an attribute (e.g., @@http.path) or via the plugin configuration to specify parent-child relationships for routing.

Example Structure:
If a Thread has many Comments:

• GET /threads/1/comments — Fetches all comments for thread 1.
• POST /threads/1/comments — Creates a comment specifically for thread 1.
• GET /threads/1/comments/2 — Fetches comment 2, but only if it belongs to thread 1 (returning 404 otherwise).

Describe alternatives you've considered

• Flat Endpoints with Filters: Using GET /comment?threadId=1. While this works, it is less RESTful and doesn't enforce the hierarchy at the routing level.
• Custom Hooks/Routes: Writing manual Next.js or Express routes to wrap the ZenStack logic. This defeats the purpose of an "Automatic" REST API and increases boilerplate.

Additional context
Hierarchical routing is a staple of mature REST frameworks. For instance:

• Ruby on Rails allows resources :threads do resources :comments end.
• NestJS and Express developers frequently implement this to improve API discoverability and security through implicit scoping.

This feature would make ZenStack-generated APIs feel significantly more professional and "opinionated" in a way that aligns with standard REST best practices.

References:

• Microsoft REST API Guidelines - Collections and Nested Resources
• Google API Design - Resource Names
• https://discord.com/channels/1035538056146595961/1087761218049167380/1460605860492476500