feat: service api add llm usage (#2051)

api/controllers/service_api/index.py

@@ -0,0 +1,16 @@
+from flask import current_app
+from flask_restful import Resource
+
+from controllers.service_api import api
+
+
+class IndexApi(Resource):
+    def get(self):
+        return {
+            "welcome": "Dify OpenAPI",
+            "api_version": "v1",
+            "server_version": current_app.config['CURRENT_VERSION']
+        }
+
+
+api.add_resource(IndexApi, '/')