Got at least one data fetching method working; turns out, we can't use a patched LogicStack to get the data

Vendor/EmbedIO-3.5.2/IHttpException.cs

@@ -0,0 +1,58 @@
+using System;
+
+namespace EmbedIO
+{
+    /// <summary>
+    /// <para>Represents an exception that results in a particular
+    /// HTTP response to be sent to the client.</para>
+    /// <para>This interface is meant to be implemented
+    /// by classes derived from <see cref="Exception" />.</para>
+    /// <para>Either as message or a data object can be attached to
+    /// the exception; which one, if any, is sent to the client
+    /// will depend upon the handler used to send the response.</para>
+    /// </summary>
+    /// <seealso cref="HttpExceptionHandlerCallback"/>
+    /// <seealso cref="HttpExceptionHandler"/>
+    public interface IHttpException
+    {
+        /// <summary>
+        /// Gets the response status code for a HTTP exception.
+        /// </summary>
+        int StatusCode { get; }
+
+        /// <summary>
+        /// Gets the stack trace of a HTTP exception.
+        /// </summary>
+        string StackTrace { get; }
+
+        /// <summary>
+        /// <para>Gets a message that can be included in the response triggered
+        /// by a HTTP exception.</para>
+        /// <para>Whether the message is actually sent to the client will depend
+        /// upon the handler used to send the response.</para>
+        /// </summary>
+        /// <remarks>
+        /// <para>Do not rely on <see cref="Exception.Message"/> to implement
+        /// this property if you want to support <see langword="null"/> messages,
+        /// because a default message will be supplied by the CLR at throw time
+        /// when <see cref="Exception.Message"/> is <see langword="null"/>.</para>
+        /// </remarks>
+        string? Message { get; }
+
+        /// <summary>
+        /// <para>Gets an object that can be serialized and included
+        /// in the response triggered by a HTTP exception.</para>
+        /// <para>Whether the object is actually sent to the client will depend
+        /// upon the handler used to send the response.</para>
+        /// </summary>
+        object? DataObject { get; }
+
+        /// <summary>
+        /// Sets necessary headers, as required by the nature
+        /// of the HTTP exception (e.g. <c>Location</c> for
+        /// <see cref="HttpRedirectException" />).
+        /// </summary>
+        /// <param name="context">The HTTP context of the response.</param>
+        void PrepareResponse(IHttpContext context);
+    }
+}