fix: get_user_threads api args

The get_user_threads api was not accepting additional arguments and there the discussion xblock wasn't working with the forum service. This PR adds args and kwargs params to the api to avoid breakage.
close #149

forum/api/threads.py

@@ -359,6 +359,7 @@ def get_user_threads(
     user_id: Optional[str] = None,
     group_id: Optional[int] = None,
     group_ids: Optional[int] = None,
+    **kwargs: Any,
 ) -> dict[str, Any]:
     """
     Get the threads for the given thread_ids.