006 add controller

app/services/aggregator.py

@@ -17,6 +17,10 @@ from app.schemas.request import DeliveryRequest
 from app.schemas.response import DeliveryPrice
 
 
+class AggregatorServiceError(RuntimeError):
+    """Base exception for AggregatorService failures."""
+
+
 class PriceCacheProtocol(Protocol):
     async def get(self, key: str) -> object | None: ...