feat: enforce jetstream ack and redelivery semantics

src/NATS.Server/JetStream/Consumers/PushConsumerEngine.cs

@@ -5,17 +5,20 @@ namespace NATS.Server.JetStream.Consumers;
 
 public sealed class PushConsumerEngine
 {
-    public void Enqueue(Queue<PushFrame> queue, StoredMessage message, ConsumerConfig config)
+    public void Enqueue(ConsumerHandle consumer, StoredMessage message)
     {
-        queue.Enqueue(new PushFrame
+        consumer.PushFrames.Enqueue(new PushFrame
         {
             IsData = true,
             Message = message,
         });
 
-        if (config.HeartbeatMs > 0)
+        if (consumer.Config.AckPolicy == AckPolicy.Explicit)
+            consumer.AckProcessor.Register(message.Sequence, consumer.Config.AckWaitMs);
+
+        if (consumer.Config.HeartbeatMs > 0)
         {
-            queue.Enqueue(new PushFrame
+            consumer.PushFrames.Enqueue(new PushFrame
             {
                 IsHeartbeat = true,
             });