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/HttpContextExtensions-RequestStream.cs

@@ -0,0 +1,61 @@
+using System.IO;
+using System.IO.Compression;
+using System.Text;
+using Swan.Logging;
+
+namespace EmbedIO
+{
+    partial class HttpContextExtensions
+    {
+        /// <summary>
+        /// <para>Wraps the request input stream and returns a <see cref="Stream"/> that can be used directly.</para>
+        /// <para>Decompression of compressed request bodies is implemented if specified in the web server's options.</para>
+        /// </summary>
+        /// <param name="this">The <see cref="IHttpContext"/> on which this method is called.</param>
+        /// <returns>
+        /// <para>A <see cref="Stream"/> that can be used to write response data.</para>
+        /// <para>This stream MUST be disposed when finished writing.</para>
+        /// </returns>
+        /// <seealso cref="OpenRequestText"/>
+        /// <seealso cref="WebServerOptionsBase.SupportCompressedRequests"/>
+        public static Stream OpenRequestStream(this IHttpContext @this)
+        {
+            var stream = @this.Request.InputStream;
+
+            var encoding = @this.Request.Headers[HttpHeaderNames.ContentEncoding]?.Trim();
+            switch (encoding)
+            {
+                case CompressionMethodNames.Gzip:
+                    if (@this.SupportCompressedRequests)
+                        return new GZipStream(stream, CompressionMode.Decompress);
+                    break;
+                case CompressionMethodNames.Deflate:
+                    if (@this.SupportCompressedRequests)
+                        return new DeflateStream(stream, CompressionMode.Decompress);
+                    break;
+                case CompressionMethodNames.None:
+                case null:
+                    return stream;
+            }
+
+            $"[{@this.Id}] Unsupported request content encoding \"{encoding}\", sending 400 Bad Request..."
+                .Warn(nameof(OpenRequestStream));
+
+            throw HttpException.BadRequest($"Unsupported content encoding \"{encoding}\"");
+        }
+
+        /// <summary>
+        /// <para>Wraps the request input stream and returns a <see cref="TextReader" /> that can be used directly.</para>
+        /// <para>Decompression of compressed request bodies is implemented if specified in the web server's options.</para>
+        /// </summary>
+        /// <param name="this">The <see cref="IHttpContext" /> on which this method is called.</param>
+        /// <returns>
+        /// <para>A <see cref="TextReader" /> that can be used to read the request body as text.</para>
+        /// <para>This reader MUST be disposed when finished reading.</para>
+        /// </returns>
+        /// <seealso cref="OpenRequestStream"/>
+        /// <seealso cref="WebServerOptionsBase.SupportCompressedRequests"/>
+        public static TextReader OpenRequestText(this IHttpContext @this)
+            => new StreamReader(OpenRequestStream(@this), @this.Request.ContentEncoding);
+    }
+}