Custom Field Validation Not Enforced in Users-Permissions Plugin
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## Bug report

### Required System information

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- Node.js version: v20.14.0
- NPM version: 10.7.0
- Strapi version: 5.4.0
- Database: mysql
- Operating system: darwin-arm64
- Is your project Javascript or Typescript: Typescript

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### Describe the bug

The issue occurs in the users-permissions plugin/extension.
I have added a custom field to the user model and configured it as both required and unique. However, when I make a POST request to create or register a user:

- If the custom field is missing from the request body, the request is still processed successfully.
- If the custom field value duplicates an existing value in the database, the request is also allowed, violating the unique constraint.

### Steps to reproduce the behavior

1.	Go to the users-permissions plugin and add a custom field to the user model.
2.	Set the field to be required and unique in the content-type settings.
3.	Use a POST request to register a new user via the /auth/local/register endpoint.
	•	Test with the custom field unset.
	•	Test with a duplicate value for the custom field.
4.	Observe the request results.

### Expected behavior

- If the custom field is missing from the request body, the API should return a validation error.
- If the custom field value duplicates an existing value in the database, the API should reject the request with a unique constraint violation error.

### Screenshots

![Screenshot Capture - 2024-11-18 - 22-32-28](https://github.com/user-attachments/assets/381fdf6d-010d-4419-b8c7-e89cf15621ce)
![Screenshot Capture - 2024-11-18 - 22-23-29](https://github.com/user-attachments/assets/af0c4233-42db-4ebc-ab66-3dcedd5ecfd7)
![Screenshot 2567-11-18 at 22 25 54](https://github.com/user-attachments/assets/57f32964-910d-4d47-af26-51594af96709)


### Code snippets

`POST /auth/local/register`
#### Duplicate Value
`
{
  "username": "testuser",
  "email": "test@example.com",
  "password": "password123",
  "customField": {{duplicate value}}
}
`

#### Missing Value
`
{
  "username": "testuser",
  "email": "test@example.com",
  "password": "password123"
}
`

### Additional context

This issue directly affects data integrity as the constraints set on the custom field (required and unique) are not being enforced.
