Add SNI support

source/Halibut/ServiceEndPoint.cs

@@ -76,6 +76,14 @@ public ServiceEndPoint(Uri baseUri, string? remoteThumbprint, ProxyDetails? prox
 
         public ProxyDetails? Proxy { get; }
 
+        /// <summary>
+        /// When set, TCP connections will be made to the host and port of this URI instead of those in
+        /// <see cref="BaseUri"/>, while the original <see cref="BaseUri"/> host is still used for TLS SNI.
+        /// This is equivalent to curl's --resolve flag and is useful when routing through a local proxy
+        /// (e.g. Toxiproxy) while preserving the correct TLS handshake.
+        /// </summary>
+        public Uri? ForceResolveHost { get; set; }
+
         public bool IsWebSocketEndpoint => IsWebSocketAddress(BaseUri);
 
         public override string ToString() => baseUriString;

source/Halibut/Transport/TcpConnectionFactory.cs

@@ -79,19 +79,21 @@ await ssl.AuthenticateAsClientAsync(
         internal static async Task<TcpClient> CreateConnectedTcpClientAsync(ServiceEndPoint endPoint, HalibutTimeoutsAndLimits halibutTimeoutsAndLimits, IStreamFactory streamFactory, ILog log, CancellationToken cancellationToken)
         {
             TcpClient client;
+            var connectHost = endPoint.ForceResolveHost?.Host ?? endPoint.BaseUri.Host;
+            var connectPort = endPoint.ForceResolveHost?.Port ?? endPoint.BaseUri.Port;
             if (endPoint.Proxy is null)
             {
                 client = CreateTcpClientAsync(halibutTimeoutsAndLimits);
-                await client.ConnectWithTimeoutAsync(endPoint.BaseUri, endPoint.TcpClientConnectTimeout, cancellationToken);
+                await client.ConnectWithTimeoutAsync(connectHost, connectPort, endPoint.TcpClientConnectTimeout, cancellationToken);
             }
             else
             {
                 log.Write(EventType.Diagnostic, "Creating a proxy client");
-                
+
                 client = await new ProxyClientFactory(streamFactory)
                     .CreateProxyClient(log, endPoint.Proxy)
                     .WithTcpClientFactory(() => CreateTcpClientAsync(halibutTimeoutsAndLimits))
-                    .CreateConnectionAsync(endPoint.BaseUri.Host, endPoint.BaseUri.Port, endPoint.TcpClientConnectTimeout, cancellationToken);
+                    .CreateConnectionAsync(connectHost, connectPort, endPoint.TcpClientConnectTimeout, cancellationToken);
             }
             return client;
         }