fix: Add setter for Chat Message History messages (#174)

Fixes mypy error:
langchain_postgres/chat_message_histories.py:344: error: Cannot override
writeable attribute with read-only property [override] Found 1 error in
1 file (checked 37 source files)

---------

Co-authored-by: Eugene Yurtsev <eyurtsev@gmail.com>

Author: averikitsch

langchain_postgres/chat_message_histories.py

@@ -340,11 +340,17 @@ async def aget_messages(self) -> List[BaseMessage]:
         messages = messages_from_dict(items)
         return messages
 
-    @property  # type: ignore[override]
+    @property
     def messages(self) -> List[BaseMessage]:
         """The abstraction required a property."""
         return self.get_messages()
 
+    @messages.setter
+    def messages(self, value: list[BaseMessage]) -> None:
+        """Clear the stored messages and appends a list of messages."""
+        self.clear()
+        self.add_messages(value)
+
     def clear(self) -> None:
         """Clear the chat message history for the GIVEN session."""
         if self._connection is None: