Add support to sync private files

Hmm, just did some more research, and it turns out that the request should be authenticated, just like everything else with entity share, simply because that's the only way to decide if a file or media entity is really available to the user or not.

So, instead of downloading from the file URI, the download should go through a route which is owned by the entity share server who does the authentication and then returns the file's content.

I am facing the same issue with private files and I am not able to sync and I got this error:

Client exception when requesting the URL: /system/files/Mahde_Test.pdf with method GET: Client error: `GET https://system/files/Mahde_Test.pdf` resulted in a `403 Forbidden` response:

I am not sure how to fix this!

The problem was because I was using this patch https://www.drupal.org/project/entity_share/issues/3275110 🐛 Entity Share Client is fails to synchronize the file if the website needs to be login. Needs work which was setting the authentication as anonymous.
Removed the patch and it works fine now!