Fix MoonshotChat instantiate with alias (#25755)

- **Description:**
   -  Fix `MoonshotChat` instantiate with alias
   - Add `MoonshotChat` to `__init__.py`

---------

Co-authored-by: Chester Curme <chester.curme@gmail.com>

libs/community/tests/integration_tests/chat_models/test_moonshot.py

@@ -1,9 +1,10 @@
 """Test Moonshot Chat Model."""
 
-from typing import Type
+from typing import Type, cast
 
 import pytest
 from langchain_core.language_models import BaseChatModel
+from langchain_core.pydantic_v1 import SecretStr
 from langchain_standard_tests.integration_tests import ChatModelIntegrationTests
 
 from langchain_community.chat_models.moonshot import MoonshotChat
@@ -21,3 +22,10 @@ class TestMoonshotChat(ChatModelIntegrationTests):
     @pytest.mark.xfail(reason="Not yet implemented.")
     def test_usage_metadata(self, model: BaseChatModel) -> None:
         super().test_usage_metadata(model)
+
+
+def test_chat_moonshot_instantiate_with_alias() -> None:
+    """Test MoonshotChat instantiate when using alias."""
+    api_key = "your-api-key"
+    chat = MoonshotChat(api_key=api_key)  # type: ignore[call-arg]
+    assert cast(SecretStr, chat.moonshot_api_key).get_secret_value() == api_key