the slug property has disappeared from my collections

Astro Info

Astro                    v5.0.0-beta.4
Node                     v20.16.0
System                   macOS (arm64)
Package Manager          yarn
Output                   static
Adapter                  @astrojs/netlify
Integrations             @astrojs/mdx
                         @astrojs/sitemap
                         load-itcss
                         @sanity/astro
                         @astrojs/preact

If this issue only occurs in one browser, which browser is a problem?

No response

Describe the Bug

I use the slug property to create static pages and all pages have stopped mounting.

In v5.0.0-beta.1 this works perfectly, but when I switch to v5.0.0-beta.4 the slug property disappears, if I use another property of the collection to mount the pages it works. I have the property inside data.

What's the expected result?

I hope to be able to use that property within data or to know if I have to find another name for the property.

Link to Minimal Reproducible Example

https://stackblitz.com/~/github.com/alberto-ln/astro-bug-slug

Participation

[ ] I am willing to submit a pull request for this issue.

withastro / astro