add base url for moonshot model (#7360)

api/core/model_runtime/model_providers/moonshot/llm/llm.py

 
     def _add_custom_parameters(self, credentials: dict) -> None:
         credentials['mode'] = 'chat'
-        credentials['endpoint_url'] = 'https://api.moonshot.cn/v1'
+        if 'endpoint_url' not in credentials or credentials['endpoint_url'] == "":
+            credentials['endpoint_url'] = 'https://api.moonshot.cn/v1'
 
     def _add_function_call(self, model: str, credentials: dict) -> None:
         model_schema = self.get_model_schema(model, credentials)

api/core/model_runtime/model_providers/moonshot/moonshot.yaml

       placeholder:
         zh_Hans: 在此输入您的 API Key
         en_US: Enter your API Key
+    - variable: endpoint_url
+      label:
+        en_US: API Base
+      type: text-input
+      required: false
+      placeholder:
+        zh_Hans: Base URL, 如：https://api.moonshot.cn/v1
+        en_US: Base URL, e.g. https://api.moonshot.cn/v1
 model_credential_schema:
   model:
     label: