feat: Added support for TuGraph graph database (#1451)

Co-authored-by: aries_ckt <916701291@qq.com>

dbgpt/datasource/base.py

@@ -216,3 +216,8 @@ class BaseConnector(ABC):
     def is_normal_type(cls) -> bool:
         """Return whether the connector is a normal type."""
         return True
+
+    @classmethod
+    def is_graph_type(cls) -> bool:
+        """Return whether the connector is a graph database connector."""
+        return False