Laravel 5.2 user spy-fields (created_by, updated_by, deleted_by) support

Model.php

<?php
namespace App\Models;

use Auth;
use Illuminate\Database\Eloquent\Model as BaseModel;

class Model extends BaseModel
{
    protected $userAttributes = [];

    public static function boot()
    {
        parent::boot();

        static::updating(function ($model) {
            if (in_array('updated_by', $model->userAttributes)) {
                $model->created_by = Auth::user()->id;
            }

        });

        static::deleting(function ($model) {
            if (in_array('deleted_by', $model->userAttributes)) {
                $model->deleted_by = Auth::user()->id;
            }
        });

        static::saving(function ($model) {
            if (in_array('created_by', $model->userAttributes)) {
                $model->created_by = Auth::user()->id;
            }
            if (in_array('updated_by', $model->userAttributes)) {
                $model->updated_by = Auth::user()->id;
            }
        });
    }
}