Add API endpoint to retrieve all guest gift reservations

Introduced a new route to fetch all guest gift reservations, ensuring API compatibility with GiftPurchase objects. Refactored CRUD functions to optimize data fetching and avoid N+1 queries. Added validation to restrict access to non-public event-related reservations.

backend/app/api/routes/events/gifts.py

@@ -1048,3 +1048,21 @@ def read_gift_purchases_by_guest(
         raise HTTPException(status_code=403, detail="Not enough permissions")
 
     return gift_purchase_crud.get_gift_reservations_by_guest(db, guest_id=guest_id)
+
+@router.get(
+    "/purchases/guest/all",
+    response_model=List[GiftPurchase],
+    operation_id="read_guests_gift_purchases"
+)
+def read_all_guest_gift_reservations(
+        *,
+        db: Session = Depends(get_db),
+) -> Any:
+    """
+    Retrieve all guest gift reservations.
+    """
+    reservations = gift_purchase_crud.get_all_guest_gift_reservations(db=db)
+
+    if not reservations:
+        reservations = []
+    return reservations