SIENTIAPDE-1110

Update get_last_data_timestamp method in Redis activity to return a string or None, improving type clarity for timestamp retrieval.

scouter/activities/redis.py

@@ -19,7 +19,7 @@ class Redis(RedisBase):
                            password, logger, notification_handler)
 
     @activity.defn(name="get_last_data_timestamp")
-    async def get_last_data_timestamp(self, input_data: dict[str, Any]) -> dict[str, Any]:
+    async def get_last_data_timestamp(self, input_data: dict[str, Any]) -> str | None:
         """
         Gets the last data timestamp from redis.
         """