refactor: The first refactored version for sdk release (#907)

Co-authored-by: chengfangyin2 <chengfangyin3@jd.com>

dbgpt/util/json_utils.py

@@ -0,0 +1,14 @@
+import json
+from datetime import date, datetime
+
+
+def serialize(obj):
+    if isinstance(obj, date):
+        return obj.isoformat()
+
+
+class DateTimeEncoder(json.JSONEncoder):
+    def default(self, obj):
+        if isinstance(obj, datetime):
+            return obj.isoformat()
+        return super().default(obj)