feat: Add Async WebRequest handler

In order to allow async/await operations to work, we need to treat the tasks differently. If the `ProcessRequest` method completes before whatever async/await operations are running complete, then the underlying connection is closed and nothing can be written to the requestor.

src/Pepperdash Core/Web/RequestHandlers/WebApiBaseRequestAsyncHandler.cs

@@ -0,0 +1,164 @@
+using Crestron.SimplSharp.WebScripting;
+using System;
+using System.Collections.Generic;
+using System.Threading.Tasks;
+
+namespace PepperDash.Core.Web.RequestHandlers
+{
+    public abstract class WebApiBaseRequestAsyncHandler:IHttpCwsHandler
+    {
+        private readonly Dictionary<string, Func<HttpCwsContext, Task>> _handlers;
+        protected readonly bool EnableCors;
+
+        /// <summary>
+        /// Constructor
+        /// </summary>
+        protected WebApiBaseRequestAsyncHandler(bool enableCors)
+        {
+            EnableCors = enableCors;
+
+            _handlers = new Dictionary<string, Func<HttpCwsContext, Task>>
+            {
+                {"CONNECT", HandleConnect},
+                {"DELETE", HandleDelete},
+                {"GET", HandleGet},
+                {"HEAD", HandleHead},
+                {"OPTIONS", HandleOptions},
+                {"PATCH", HandlePatch},
+                {"POST", HandlePost},
+                {"PUT", HandlePut},
+                {"TRACE", HandleTrace}
+            };
+        }
+
+        /// <summary>
+        /// Constructor
+        /// </summary>
+        protected WebApiBaseRequestAsyncHandler()
+            : this(false)
+        {
+        }
+
+        /// <summary>
+        /// Handles CONNECT method requests
+        /// </summary>
+        /// <param name="context"></param>
+        protected virtual async Task HandleConnect(HttpCwsContext context)
+        {
+            context.Response.StatusCode = 501;
+            context.Response.StatusDescription = "Not Implemented";
+            context.Response.End();            
+        }
+
+        /// <summary>
+        /// Handles DELETE method requests
+        /// </summary>
+        /// <param name="context"></param>
+        protected virtual async Task HandleDelete(HttpCwsContext context)
+        {
+            context.Response.StatusCode = 501;
+            context.Response.StatusDescription = "Not Implemented";
+            context.Response.End();
+        }
+
+        /// <summary>
+        /// Handles GET method requests
+        /// </summary>
+        /// <param name="context"></param>
+        protected virtual async Task HandleGet(HttpCwsContext context)
+        {
+            context.Response.StatusCode = 501;
+            context.Response.StatusDescription = "Not Implemented";
+            context.Response.End();
+        }
+
+        /// <summary>
+        /// Handles HEAD method requests
+        /// </summary>
+        /// <param name="context"></param>
+        protected virtual async Task HandleHead(HttpCwsContext context)
+        {
+            context.Response.StatusCode = 501;
+            context.Response.StatusDescription = "Not Implemented";
+            context.Response.End();
+        }
+
+        /// <summary>
+        /// Handles OPTIONS method requests
+        /// </summary>
+        /// <param name="context"></param>
+        protected virtual async Task HandleOptions(HttpCwsContext context)
+        {
+            context.Response.StatusCode = 501;
+            context.Response.StatusDescription = "Not Implemented";
+            context.Response.End();
+        }
+
+        /// <summary>
+        /// Handles PATCH method requests
+        /// </summary>
+        /// <param name="context"></param>
+        protected virtual async Task HandlePatch(HttpCwsContext context)
+        {
+            context.Response.StatusCode = 501;
+            context.Response.StatusDescription = "Not Implemented";
+            context.Response.End();
+        }
+
+        /// <summary>
+        /// Handles POST method requests
+        /// </summary>
+        /// <param name="context"></param>
+        protected virtual async Task HandlePost(HttpCwsContext context)
+        {
+            context.Response.StatusCode = 501;
+            context.Response.StatusDescription = "Not Implemented";
+            context.Response.End();
+        }
+
+        /// <summary>
+        /// Handles PUT method requests
+        /// </summary>
+        /// <param name="context"></param>
+        protected virtual async Task HandlePut(HttpCwsContext context)
+        {
+            context.Response.StatusCode = 501;
+            context.Response.StatusDescription = "Not Implemented";
+            context.Response.End();
+        }
+
+        /// <summary>
+        /// Handles TRACE method requests
+        /// </summary>
+        /// <param name="context"></param>
+        protected virtual async Task HandleTrace(HttpCwsContext context)
+        {
+            context.Response.StatusCode = 501;
+            context.Response.StatusDescription = "Not Implemented";
+            context.Response.End();
+        }
+
+        /// <summary>
+        /// Process request
+        /// </summary>
+        /// <param name="context"></param>
+        public void ProcessRequest(HttpCwsContext context)
+        {
+            if (!_handlers.TryGetValue(context.Request.HttpMethod, out Func<HttpCwsContext, Task> handler))
+            {
+                return;
+            }
+
+            if (EnableCors)
+            {
+                context.Response.Headers.Add("Access-Control-Allow-Origin", "*");
+                context.Response.Headers.Add("Access-Control-Allow-Methods", "POST, GET, OPTIONS");
+            }
+
+            var handlerTask = handler(context);
+
+            handlerTask.Wait();
+        }
+    }
+}
+}