Add NatsPayloadTooLargeException class (#761)

* Add NatsPayloadTooLargeException.
Fix #759

* Fix unittest

---------

Co-authored-by: Ziya Suzen <ziya@suzen.net>

Author: aDisplayName

src/NATS.Client.Core/Commands/CommandWriter.cs

@@ -323,7 +323,7 @@ public ValueTask PublishAsync<T>(string subject, T? value, NatsHeaders? headers,
             var size = payloadBuffer.WrittenMemory.Length + (headersBuffer?.WrittenMemory.Length ?? 0);
             if (_connection.ServerInfo is { } info && size > info.MaxPayload)
             {
-                throw new NatsException($"Payload size {size} exceeds server's maximum payload size {info.MaxPayload}");
+                throw new NatsPayloadTooLargeException($"Payload size {size} exceeds server's maximum payload size {info.MaxPayload}");
             }
         }
         catch

src/NATS.Client.Core/NatsException.cs

@@ -50,3 +50,11 @@ public NatsServerException(string error)
 
     public bool IsAuthError { get; }
 }
+
+public sealed class NatsPayloadTooLargeException : NatsException
+{
+    public NatsPayloadTooLargeException(string error)
+        : base(error)
+    {
+    }
+}

tests/NATS.Client.Core2.Tests/ProtocolTest.cs

@@ -443,7 +443,7 @@ await Retry.Until(
 
         {
             var payload = new byte[nats.ServerInfo!.MaxPayload + 1];
-            var exception = await Assert.ThrowsAsync<NatsException>(async () =>
+            var exception = await Assert.ThrowsAsync<NatsPayloadTooLargeException>(async () =>
                 await nats.PublishAsync("foo.none", payload, cancellationToken: cts.Token));
             Assert.Matches(@"Payload size \d+ exceeds server's maximum payload size \d+", exception.Message);
         }