feat(fetch-router): support nested routes in createResource & createResources

[MichaelDeBoey]

With this PR

  let books = {
    ...resources('books'),
    author: 'books/:id/author',
    reviews: resources('books/:id/reviews', { param: 'reviewId' }),
  }
  let profile = {
    ...resource('profile'),
    admin: '/profile/admin',
    todos: resource('profile/todos'),
  }

now becomes

let books = resources('books', {
  children: { author: 'author', reviews: resources('reviews', { param: 'reviewId' }) },
})
let profile = resource('profile', { children: { admin: 'admin', todos: resource('todos') } })

[Copilot]

Pull Request Overview

This PR adds support for nested routes in createResource and createResources functions through a new children option, allowing developers to define child routes inline instead of using object spread syntax.

• Adds children option to both ResourceOptions and ResourcesOptions interfaces
• Implements addParamToPatterns utility function to prepend parameters to child route patterns
• Updates type definitions to handle nested route structures with proper parameter inheritance

Reviewed Changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 1 comment.

File	Description
packages/fetch-router/src/lib/resource.ts	Adds children option support, implements parameter prefixing logic, and updates type definitions
packages/fetch-router/src/lib/resource.test.ts	Adds comprehensive tests for the new children functionality with various route pattern types
packages/fetch-router/CHANGELOG.md	Documents the new nested routes feature with before/after examples

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[Copilot]

The type assertion (value as any).pattern on line 143 bypasses TypeScript's type checking. Consider using a more specific type guard or conditional type checking to ensure type safety.

[MichaelDeBoey]

This is also done in a couple of other places, hence why I took it over.

If needed, I'm happy to add better typing here

[mjackson]

Thanks for the PR, @MichaelDeBoey. I think I prefer the object spread syntax here instead of a children config key to resource/resources. This way we keep the composition of the routes object under the full control of the user without adding in more API that requires us to merge children objects in.