✨(back) new endpoint document can_edit

The endpoint can_edit is added to the DocumentViewset, it will give the
information to the frontend application id the current user can edit the
Docs based on the no-websocket rules.

src/backend/core/models.py

@@ -836,6 +836,7 @@ class Document(MP_Node, BaseModel):
             "ai_translate": ai_access,
             "attachment_upload": can_update,
             "media_check": can_get,
+            "can_edit": can_update,
             "children_list": can_get,
             "children_create": can_update and user.is_authenticated,
             "collaboration_auth": can_get,