aggregate requests (#328)

src/litserve/server.py

@@ -308,7 +308,7 @@ async def data_streamer(self, q: deque, data_available: asyncio.Event, send_stat
     @property
     def active_requests(self):
         if self.track_requests and self.active_counters:
-            return self.active_counters[self.app.response_queue_id].value
+            return sum(counter.value for counter in self.active_counters)
         warnings.warn(
             "Active request counter is not enabled while using `on_request` callback hook. "
             "Please set track_requests=True in the LitServer."