✨(backend) add new ability on document "accesses_view"

We need this ability in the frontend to know whether we should try
to display the list of users who have document accesses. If this
ability is False (e.g for anonymous users), we should only show
the link reach and link role when clicking on the "Share" button.

CHANGELOG.md

@@ -15,6 +15,7 @@ and this project adheres to
 - 🌐(frontend) add localization to editor #268
 - ✨Public and restricted doc editable #357
 - ✨(frontend) Add full name if available #380
+- ✨(backend) Add view accesses ability #376
 
 ## Fixed