chore: Add GroupConsumer Stats()

group_consumer.go

@@ -157,6 +157,14 @@ func (gc *GroupConsumer[T]) Close() []InnerAck {
 	return gc.lostAcks
 }
 
+// Fetch basic stats about buffers:
+// 1. Number of fetched entries
+// 2. Number of pending acks
+// 3. Number of unprocessed ack errors
+func (gc *GroupConsumer[T]) Stats() (int, int, int) {
+	return len(gc.fetchChan), len(gc.ackChan), len(gc.ackErrChan)
+}
+
 // consumeLoop fills the consumeChan with new messages from all sources.
 // It is the last goroutine to exit and does remaing ack message recovery.
 func (gc *GroupConsumer[T]) consumeLoop() {