如何验证Laravel中两个字段的唯一组合？

public function rules()
{
    return [
        'email' => 'required|email',
        'username' => 'required',
        'email_username' => Rule::unique('users')->where(function ($query) {
            return $query->where('email', $this->email)
                         ->where('username', $this->username);
        }),
    ];
}

public function store(Request $request)
{
    $validatedData = $request->validate([
        'email' => 'required|email',
        'username' => 'required',
        'email_username' => Rule::unique('users')->where(function ($query) use ($request) {
            return $query->where('email', $request->email)
                         ->where('username', $request->username);
        }),
    ]);

    // 其他处理逻辑
}