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/KestrelInMemoryTest.cs

@@ -0,0 +1,38 @@
+using Microsoft.AspNetCore.Builder;
+using Microsoft.AspNetCore.Connections;
+using Microsoft.Extensions.DependencyInjection;
+using Microsoft.Extensions.DependencyInjection.Extensions;
+
+namespace ModelContextProtocol.Tests.Utils;
+
+public class KestrelInMemoryTest : LoggedTest
+{
+    private readonly KestrelInMemoryTransport _inMemoryTransport = new();
+
+    public KestrelInMemoryTest(ITestOutputHelper testOutputHelper)
+        : base(testOutputHelper)
+    {
+        // Use SlimBuilder instead of EmptyBuilder to avoid having to call UseRouting() and UseEndpoints(_ => { })
+        // or a helper that does the same every test. But clear out the existing socket transport to avoid potential port conflicts.
+        Builder = WebApplication.CreateSlimBuilder();
+        Builder.Services.RemoveAll<IConnectionListenerFactory>();
+        Builder.Services.AddSingleton<IConnectionListenerFactory>(_inMemoryTransport);
+        Builder.Services.AddSingleton(LoggerProvider);
+    }
+
+    public WebApplicationBuilder Builder { get; }
+
+    public HttpClient CreateHttpClient()
+    {
+        var socketsHttpHandler = new SocketsHttpHandler()
+        {
+            ConnectCallback = (context, token) =>
+            {
+                var connection = _inMemoryTransport.CreateConnection();
+                return new(connection.ClientStream);
+            },
+        };
+
+        return new HttpClient(socketsHttpHandler);
+    }
+}