Use Kestrel for all in-memory HTTP tests (#225)

* Add route pattern parameter to MapMcp
* Add configureOptionsAsync
* Use Kestrel for all in-memory HTTP tests
* Use ApplicationStopping token for SSE responses
* Use RegisterNotificationHandler in MapMcp tests
* Work around SocketsHttpHandler bug where it doesn't call DispseAsync on the stream returned by the ConnectCallback

tests/ModelContextProtocol.Tests/Utils/KestrelInMemoryTransport.cs

@@ -0,0 +1,50 @@
+using Microsoft.AspNetCore.Connections;
+using System.Net;
+using System.Threading.Channels;
+
+namespace ModelContextProtocol.Tests.Utils;
+
+public sealed class KestrelInMemoryTransport : IConnectionListenerFactory, IConnectionListener
+{
+    private readonly Channel<ConnectionContext> _acceptQueue = Channel.CreateUnbounded<ConnectionContext>();
+    private EndPoint? _endPoint;
+
+    public EndPoint EndPoint => _endPoint ?? throw new InvalidOperationException("EndPoint is not set. Call BindAsync first.");
+
+    public KestrelInMemoryConnection CreateConnection()
+    {
+        var connection = new KestrelInMemoryConnection();
+        _acceptQueue.Writer.TryWrite(connection);
+        return connection;
+    }
+
+    public async ValueTask<ConnectionContext?> AcceptAsync(CancellationToken cancellationToken = default)
+    {
+        if (await _acceptQueue.Reader.WaitToReadAsync(cancellationToken))
+        {
+            while (_acceptQueue.Reader.TryRead(out var item))
+            {
+                return item;
+            }
+        }
+
+        return null;
+    }
+
+    public ValueTask<IConnectionListener> BindAsync(EndPoint endpoint, CancellationToken cancellationToken = default)
+    {
+        _endPoint = endpoint;
+        return new ValueTask<IConnectionListener>(this);
+    }
+
+    public ValueTask DisposeAsync()
+    {
+        return UnbindAsync(default);
+    }
+
+    public ValueTask UnbindAsync(CancellationToken cancellationToken = default)
+    {
+        _acceptQueue.Writer.TryComplete();
+        return default;
+    }
+}