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/Routing/RouteResolverCollectionBase`2.cs

@@ -0,0 +1,150 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Threading.Tasks;
+using EmbedIO.Internal;
+using EmbedIO.Utilities;
+using Swan;
+using Swan.Collections;
+using Swan.Configuration;
+
+namespace EmbedIO.Routing
+{
+    /// <summary>
+    /// Implements the logic for resolving a context and a URL path against a list of routes,
+    /// possibly handling different HTTP methods via different handlers.
+    /// </summary>
+    /// <typeparam name="TData">The type of the data used to select a suitable handler
+    /// for a context.</typeparam>
+    /// <typeparam name="TResolver">The type of the route resolver.</typeparam>
+    /// <seealso cref="Utilities.ComponentCollection{T}" />
+    public abstract class RouteResolverCollectionBase<TData, TResolver> : ConfiguredObject
+        where TResolver : RouteResolverBase<TData>
+    {
+        private readonly List<TResolver> _resolvers = new List<TResolver>();
+
+        /// <summary>
+        /// Associates some data and a route to a handler.
+        /// </summary>
+        /// <param name="data">Data used to determine which contexts are
+        /// suitable to be handled by <paramref name="handler"/>.</param>
+        /// <param name="matcher">The <see cref="RouteMatcher"/>to match URL paths against.</param>
+        /// <param name="handler">A callback used to handle matching contexts.</param>
+        /// <exception cref="ArgumentNullException">
+        /// <para><paramref name="matcher"/> is <see langword="null"/>.</para>
+        /// <para>- or -</para>
+        /// <para><paramref name="handler"/> is <see langword="null"/>.</para>
+        /// </exception>
+        /// <exception cref="InvalidOperationException">The <see cref="CreateResolver"/> method
+        /// returned <see langword="null"/>.</exception>
+        /// <seealso cref="ResolveAsync"/>
+        /// <seealso cref="Add(TData,RouteMatcher,SyncRouteHandlerCallback)"/>
+        /// <seealso cref="RouteResolverBase{TData}.Add(TData,RouteHandlerCallback)"/>
+        public void Add(TData data, RouteMatcher matcher, RouteHandlerCallback handler)
+        {
+            matcher = Validate.NotNull(nameof(matcher), matcher);
+            handler = Validate.NotNull(nameof(handler), handler);
+            GetResolver(matcher).Add(data, handler);
+        }
+
+        /// <summary>
+        /// Associates some data and a route to a synchronous handler.
+        /// </summary>
+        /// <param name="data">Data used to determine which contexts are
+        /// suitable to be handled by <paramref name="handler"/>.</param>
+        /// <param name="matcher">The <see cref="RouteMatcher"/>to match URL paths against.</param>
+        /// <param name="handler">A callback used to handle matching contexts.</param>
+        /// <exception cref="ArgumentNullException">
+        /// <para><paramref name="matcher"/> is <see langword="null"/>.</para>
+        /// <para>- or -</para>
+        /// <para><paramref name="handler"/> is <see langword="null"/>.</para>
+        /// </exception>
+        /// <exception cref="InvalidOperationException">The <see cref="CreateResolver"/> method
+        /// returned <see langword="null"/>.</exception>
+        /// <seealso cref="ResolveAsync"/>
+        /// <seealso cref="Add(TData,RouteMatcher,RouteHandlerCallback)"/>
+        /// <seealso cref="RouteResolverBase{TData}.Add(TData,SyncRouteHandlerCallback)"/>
+        public void Add(TData data, RouteMatcher matcher, SyncRouteHandlerCallback handler)
+        {
+            matcher = Validate.NotNull(nameof(matcher), matcher);
+            handler = Validate.NotNull(nameof(handler), handler);
+            GetResolver(matcher).Add(data, handler);
+        }
+
+        /// <summary>
+        /// Asynchronously matches a URL path against <see cref="Route"/>;
+        /// if the match is successful, tries to handle the specified <paramref name="context"/>
+        /// using handlers selected according to data extracted from the context.
+        /// <para>Registered resolvers are tried in the same order they were added by calling
+        /// <see cref="Utilities.IComponentCollection{T}.Add"/>.</para>
+        /// </summary>
+        /// <param name="context">The context to handle.</param>
+        /// <returns>A <see cref="Task"/>, representing the ongoing operation,
+        /// that will return a result in the form of one of the <see cref="RouteResolutionResult"/> constants.</returns>
+        /// <seealso cref="RouteResolverBase{TData}.ResolveAsync"/>
+        public async Task<RouteResolutionResult> ResolveAsync(IHttpContext context)
+        {
+            var result = RouteResolutionResult.RouteNotMatched;
+            foreach (var resolver in _resolvers)
+            {
+                var resolverResult = await resolver.ResolveAsync(context).ConfigureAwait(false);
+                OnResolverCalled(context, resolver, resolverResult);
+                if (resolverResult == RouteResolutionResult.Success)
+                    return RouteResolutionResult.Success;
+
+                // This is why RouteResolutionResult constants must not be reordered.
+                if (resolverResult > result)
+                    result = resolverResult;
+            }
+
+            return result;
+        }
+
+        /// <summary>
+        /// Locks this collection, preventing further additions.
+        /// </summary>
+        public void Lock() => LockConfiguration();
+
+        /// <inheritdoc />
+        protected override void OnBeforeLockConfiguration()
+        {
+            foreach (var resolver in _resolvers)
+                resolver.Lock();
+        }
+
+        /// <summary>
+        /// <para>Called by <see cref="Add(TData,RouteMatcher,RouteHandlerCallback)"/>
+        /// and <see cref="Add(TData,RouteMatcher,SyncRouteHandlerCallback)"/> to create an instance
+        /// of <typeparamref name="TResolver"/> that can resolve the specified route.</para>
+        /// <para>If this method returns <see langword="null"/>, an <see cref="InvalidOperationException"/>
+        /// is thrown by the calling method.</para>
+        /// </summary>
+        /// <param name="matcher">The <see cref="RouteMatcher"/>to match URL paths against.</param>
+        /// <returns>A newly-constructed instance of <typeparamref name="TResolver"/>.</returns>
+        protected abstract TResolver CreateResolver(RouteMatcher matcher);
+        
+        /// <summary>
+        /// <para>Called by <see cref="ResolveAsync"/> when a resolver's
+        /// <see cref="RouteResolverBase{TData}.ResolveAsync">ResolveAsync</see> method has been called
+        /// to resolve a context.</para>
+        /// <para>This callback method may be used e.g. for logging or testing.</para>
+        /// </summary>
+        /// <param name="context">The context to handle.</param>
+        /// <param name="resolver">The resolver just called.</param>
+        /// <param name="result">The result returned by <paramref name="resolver"/>.<see cref="RouteResolverBase{TData}.ResolveAsync">ResolveAsync</see>.</param>
+        protected virtual void OnResolverCalled(IHttpContext context, TResolver resolver, RouteResolutionResult result)
+        {
+        }
+
+        private TResolver GetResolver(RouteMatcher matcher)
+        {
+            var resolver = _resolvers.FirstOrDefault(r => r.Matcher.Equals(matcher));
+            if (resolver != null)
+                return resolver;
+
+            resolver = CreateResolver(matcher);
+            _resolvers.Add(resolver ?? throw SelfCheck.Failure($"{nameof(CreateResolver)} returned null."));
+            return resolver;
+        }
+    }
+}