Find a way to allow unserialize classes

Please check, it's my first patch

@lamp5 Please explain in more detail what and why is getting unserialized?

@Ihnatsevych This would simply undo 📌 unserialize() is insecure unless allowed classes are limited. Use a safe format like JSON or use the allowed_classes option. Fixed and I don't think it's what we want.

@gbyte
This patch doesn't introduce anything new, but it allows other modules to reference the complete unserialized classes, as it was in previous versions of the module.
Since I am not facing the problem described in the parent issue, this patch helps me generate sitemaps

Few years ago we decided to use simple_sitemap for our project. We are generating a few types of sitemap so we have few of plugin managers to mange types. In our case, we serialized class objects to simple_sitemap queue items and after this update our whole sitemap system stopped working. It was a reason why I opened this issue to find a smart way without patches like we can see here and without expensive refactor of our project.

We are also experiencing this issue with core Media classes being stored in the queue items.
The patch #4, works as a workaround.

After re-reviewing this, we updated our UrlGenerator plugin to not store the actual entities in the queue items as this wasn't a good idea in the first place I think. We now just store the entity id in the queue item and load each entity on-demand when the queue item is processed.

@kriboogh Please provide a merge request with your changes.

@gbyte, well actually we don't need the patch anymore, because I rewrote our code to deal with the queue differently.
(But it was the patch from @Ihnatsevych #4 that initially worked).

@gbyte, well actually we don't need the patch anymore, because I rewrote our code to deal with the queue differently.

Ah got you - it's your plugin that you rewrote. I was asking for a patch because I was under the impression you were referring to one of the default plugins (which I remember have not been storing entities in the queue for a long time).

I also rewrote my whole project to avoid serialize objects of class so we can mark this issue like "works as designed"