copy product with pydantic model_copy instead of copy.deepcopy (#109)

Author: Phil Varner

src/stapi_fastapi/models/product.py

@@ -1,6 +1,5 @@
 from __future__ import annotations
 
-from copy import deepcopy
 from enum import Enum
 from typing import TYPE_CHECKING, Literal, Optional, Self
 
@@ -78,7 +77,7 @@ def with_links(self: Self, links: list[Link] | None = None) -> Self:
         if not links:
             return self
 
-        new = deepcopy(self)
+        new = self.model_copy(deep=True)
         new.links.extend(links)
         return new