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/HttpExceptionHandlerCallback.cs

@@ -0,0 +1,21 @@
+using System.Threading.Tasks;
+
+namespace EmbedIO
+{
+    /// <summary>
+    /// A callback used to build the contents of the response for an <see cref="IHttpException" />.
+    /// </summary>
+    /// <param name="context">An <see cref="IHttpContext" /> interface representing the context of the request.</param>
+    /// <param name="httpException">An <see cref="IHttpException" /> interface.</param>
+    /// <returns>A <see cref="Task" /> representing the ongoing operation.</returns>
+    /// <remarks>
+    /// <para>When this delegate is called, the response's status code has already been set and the <see cref="IHttpException.PrepareResponse"/>
+    /// method has already been called. The only thing left to do is preparing the response's content, according
+    /// to the <see cref="IHttpException.Message"/> property.</para>
+    /// <para>Any exception thrown by a handler (even a HTTP exception) will go unhandled: the web server
+    /// will not crash, but processing of the request will be aborted, and the response will be flushed as-is.
+    /// In other words, it is not a good ides to <c>throw HttpException.NotFound()</c> (or similar)
+    /// from a handler.</para>
+    /// </remarks>
+    public delegate Task HttpExceptionHandlerCallback(IHttpContext context, IHttpException httpException);
+}