feat: implement /subz endpoint with account filter, test subject, and pagination

src/NATS.Server/Subscriptions/SubList.cs

@@ -33,6 +33,62 @@ public sealed class SubList : IDisposable
         }
     }
 
+    /// <summary>
+    /// Returns all subscriptions in the trie. For monitoring only.
+    /// </summary>
+    public List<Subscription> GetAllSubscriptions()
+    {
+        _lock.EnterReadLock();
+        try
+        {
+            var result = new List<Subscription>();
+            CollectAll(_root, result);
+            return result;
+        }
+        finally
+        {
+            _lock.ExitReadLock();
+        }
+    }
+
+    private static void CollectAll(TrieLevel level, List<Subscription> result)
+    {
+        foreach (var (_, node) in level.Nodes)
+        {
+            foreach (var sub in node.PlainSubs) result.Add(sub);
+            foreach (var (_, qset) in node.QueueSubs)
+                foreach (var sub in qset) result.Add(sub);
+            if (node.Next != null) CollectAll(node.Next, result);
+        }
+        if (level.Pwc != null)
+        {
+            foreach (var sub in level.Pwc.PlainSubs) result.Add(sub);
+            foreach (var (_, qset) in level.Pwc.QueueSubs)
+                foreach (var sub in qset) result.Add(sub);
+            if (level.Pwc.Next != null) CollectAll(level.Pwc.Next, result);
+        }
+        if (level.Fwc != null)
+        {
+            foreach (var sub in level.Fwc.PlainSubs) result.Add(sub);
+            foreach (var (_, qset) in level.Fwc.QueueSubs)
+                foreach (var sub in qset) result.Add(sub);
+            if (level.Fwc.Next != null) CollectAll(level.Fwc.Next, result);
+        }
+    }
+
+    /// <summary>
+    /// Returns the current number of entries in the cache.
+    /// </summary>
+    public int CacheCount
+    {
+        get
+        {
+            _lock.EnterReadLock();
+            try { return _cache?.Count ?? 0; }
+            finally { _lock.ExitReadLock(); }
+        }
+    }
+
     public void Insert(Subscription sub)
     {
         var subject = sub.Subject;