Relation properties missing in Swagger json in the documentation plugin
### Node Version

20.11.0

### NPM/Yarn/PNPM Version

Yarn 1.22.19

### Strapi Version

5.9.0

### Operating System

MacOS

### Database

SQLite

### Javascript or Typescript

Typescript

### Reproduction URL

_No response_

### Bug Description

Relations are missing their json content in the swagger file from the documentation plugin. In version 4 I was able to see what properties where in my relations.

Here you can see Strapi v4:
<img width="444" alt="Image" src="https://github.com/user-attachments/assets/0cbc35d1-6fc3-494e-be09-8918d6af1502" />

Here you can see Strapi v5:
<img width="459" alt="Image" src="https://github.com/user-attachments/assets/ebbf7efd-33de-4a6b-988b-476338db7544" />

As you can see there are no properties in my `at_homepage_single_reviews` relation besides `id` and `documentId`. In the image from version 4 you can see more properties.

### Steps to Reproduce

1. Create a component with a relation.
2. Check this in the swagger file in Strapi v4
3. Check this in the swagger file in Strapi v5

### Expected Behavior

All properties are shown in a relation

### Logs

```shell

```

### Code Snippets

_No response_

### Media

_No response_

### Additional information

_No response_

### Confirmation Checklist

- [x] I have checked the existing [issues](https://github.com/strapi/strapi/issues) for duplicates.
- [x] I agree to follow this project's [Code of Conduct](https://github.com/strapi/strapi/blob/develop/CODE_OF_CONDUCT.md).