如何在Laravel请求中返回相关表中的ID字段

namespace App\Models;

use Illuminate\Database\Eloquent\Model;

class User extends Model
{
    public function posts()
    {
        return $this->hasMany(Post::class);
    }
}

namespace App\Models;

use Illuminate\Database\Eloquent\Model;

class Post extends Model
{
    public function user()
    {
        return $this->belongsTo(User::class);
    }
}

namespace App\Http\Controllers;

use App\Models\User;
use Illuminate\Http\Request;

class UserController extends Controller
{
    public function show($id)
    {
        $user = User::with('posts')->findOrFail($id);

        $postIds = $user->posts->pluck('id');

        return response()->json($postIds);
    }
}