feat: Oracle Canvas, Revision History and Canvas Sharing (#33)

Co-authored-by: Sagnik <sagnik7896@gmail.com>
Reviewed-on: #33

backend/oracle/router_v1.py

@@ -257,13 +257,16 @@ async def create_fork(
     page = await canvas_service.get_page(page_id, ctx.tenant_id)
     if not page:
         raise HTTPException(status_code=404, detail="Source page not found.")
-    fork = await collaboration_service.create_fork(
-        source_page=page,
-        recipient_user_id=payload.recipientUserId,
-        created_by=ctx.actor_id,
-        visibility=payload.visibility,
-        message=payload.message,
-    )
+    try:
+        fork = await collaboration_service.create_fork(
+            source_page=page,
+            recipient_user_id=payload.recipientUserId,
+            created_by=ctx.actor_id,
+            visibility=payload.visibility,
+            message=payload.message,
+        )
+    except ValueError as exc:
+        raise HTTPException(status_code=400, detail=str(exc)) from exc
     return _ok(fork)