phpvms/app/Http/Requests/CreateUserRequest.php

<?php

namespace App\Http\Requests;

use App\Models\User;
use Illuminate\Foundation\Http\FormRequest;

class CreateUserRequest extends FormRequest
{

    /**
     * Determine if the user is authorized to make this request.
     *
     * @return bool
     */
    public function authorize()
    {
        return true;
    }

    /**
     * Get the validation rules that apply to the request.
     *
     * @return array
     */
    public function rules()
    {
        $rules = User::$rules;
        $rules['email'] .= '|unique:users,email';
        return $rules;
    }
}