Fix several problems with gift registry api

backend/app/crud/base.py

@@ -1,4 +1,6 @@
 from typing import Any, Dict, Generic, List, Optional, Type, TypeVar, Union
+from uuid import UUID
+
 from fastapi.encoders import jsonable_encoder
 from pydantic import BaseModel
 from sqlalchemy.orm import Session
@@ -19,7 +21,7 @@ class CRUDBase(Generic[ModelType, CreateSchemaType, UpdateSchemaType]):
         """
         self.model = model
 
-    def get(self, db: Session, id: str) -> Optional[ModelType]:
+    def get(self, db: Session, id: UUID | str) -> Optional[ModelType]:
         return db.query(self.model).filter(self.model.id == id).first()
 
     def get_multi(