added update to comments with characters counter

backend/app/schemas.py

@@ -1,5 +1,5 @@
 from typing import List, Optional
-from pydantic import BaseModel, EmailStr
+from pydantic import BaseModel, EmailStr, constr
 from datetime import date
 
 
@@ -120,7 +120,7 @@ class ShipmentCreate(BaseModel):
     shipment_name: str
     shipment_date: date
     shipment_status: str
-    comments: Optional[str] = ""
+    comments: Optional[constr(max_length=500)]
     contact_person_id: int
     return_address_id: int
     proposal_id: int