feat: execute post-baseline jetstream parity plan

tests/NATS.Server.Tests/JetStreamCrossClusterGatewayParityTests.cs

@@ -0,0 +1,26 @@
+using Microsoft.Extensions.Logging.Abstractions;
+using NATS.Server.Configuration;
+using NATS.Server.Gateways;
+
+namespace NATS.Server.Tests;
+
+public class JetStreamCrossClusterGatewayParityTests
+{
+    [Fact]
+    public async Task Cross_cluster_jetstream_messages_use_gateway_forwarding_path()
+    {
+        var manager = new GatewayManager(
+            new GatewayOptions { Name = "GW", Host = "127.0.0.1", Port = 0 },
+            new ServerStats(),
+            "S1",
+            _ => { },
+            _ => { },
+            NullLogger<GatewayManager>.Instance);
+
+        await manager.ForwardJetStreamClusterMessageAsync(
+            new GatewayMessage("$JS.CLUSTER.REPL.ORDERS", null, "x"u8.ToArray()),
+            default);
+
+        manager.ForwardedJetStreamClusterMessages.ShouldBe(1);
+    }
+}