fix: MoonshotChat fails when setting the moonshot_api_key through the OS environment. (#23176)

Close #23174

Co-authored-by: tianming <tianming@bytenew.com>

libs/community/langchain_community/chat_models/moonshot.py

@@ -2,7 +2,10 @@
 from typing import Dict
 
 from langchain_core.pydantic_v1 import root_validator
-from langchain_core.utils import get_from_dict_or_env
+from langchain_core.utils import (
+    convert_to_secret_str,
+    get_from_dict_or_env,
+)
 
 from langchain_community.chat_models import ChatOpenAI
 from langchain_community.llms.moonshot import MOONSHOT_SERVICE_URL_BASE, MoonshotCommon
@@ -28,8 +31,8 @@ class MoonshotChat(MoonshotCommon, ChatOpenAI):  # type: ignore[misc]
     @root_validator()
     def validate_environment(cls, values: Dict) -> Dict:
         """Validate that the environment is set up correctly."""
-        values["moonshot_api_key"] = get_from_dict_or_env(
-            values, "moonshot_api_key", "MOONSHOT_API_KEY"
+        values["moonshot_api_key"] = convert_to_secret_str(
+            get_from_dict_or_env(values, "moonshot_api_key", "MOONSHOT_API_KEY")
         )
 
         try: