如何在Laravel上建立无主键的users表与other的关系

namespace App;

use Illuminate\Database\Eloquent\Model;

class User extends Model
{
    protected $table = 'users';
    protected $primaryKey = null;
    public $timestamps = false;
}

namespace App;

use Illuminate\Database\Eloquent\Model;

class User extends Model
{
    protected $table = 'users';
    protected $primaryKey = null;
    public $timestamps = false;

    public function other()
    {
        return $this->hasOne(Other::class, 'user_id');
    }
}

namespace App;

use Illuminate\Database\Eloquent\Model;

class Other extends Model
{
    protected $table = 'other';
    public $timestamps = false;

    public function user()
    {
        return $this->belongsTo(User::class, 'user_id');
    }
}

$user = User::find(1);
$other = $user->other;