Disable trailing slash redirect for webpanel

Fixes #1761

src/Tgstation.Server.Host/Controllers/ControlPanelController.cs

@@ -30,6 +30,11 @@ namespace Tgstation.Server.Host.Controllers
 		/// </summary>
 		public const string ControlPanelRoute = "/app";
 
+		/// <summary>
+		/// The route to the control panel channel .json.
+		/// </summary>
+		public const string ChannelJsonRoute = "channel.json";
+
 		/// <summary>
 		/// Header for forcing channel.json to be fetched.
 		/// </summary>
@@ -70,7 +75,7 @@ namespace Tgstation.Server.Host.Controllers
 		/// Returns the <see cref="ControlPanelConfiguration.Channel"/>.
 		/// </summary>
 		/// <returns>A <see cref="JsonResult"/> with the <see cref="ControlPanelConfiguration.Channel"/>.</returns>
-		[Route("channel.json")]
+		[Route(ChannelJsonRoute)]
 		[HttpGet]
 		public IActionResult GetChannelJson()
 		{

src/Tgstation.Server.Host/Controllers/RootController.cs

@@ -1,5 +1,6 @@
 using System;
 using System.Collections.Generic;
+using System.Linq.Expressions;
 
 using Microsoft.AspNetCore.Authorization;
 using Microsoft.AspNetCore.Hosting;
@@ -61,6 +62,27 @@ namespace Tgstation.Server.Host.Controllers
 		/// </summary>
 		readonly ControlPanelConfiguration controlPanelConfiguration;
 
+		/// <summary>
+		/// Gets a <see cref="Tuple{T1, T2}"/> giving the <see cref="ControlPanelController"/> and action names for a given <paramref name="actionExpression"/>.
+		/// </summary>
+		/// <param name="actionExpression">An expression invoking the action on <see cref="ControlPanelController"/>.</param>
+		/// <returns>A <see cref="Tuple{T1, T2}"/> containing the controller and action names.</returns>
+		static Tuple<string, string?> GetControlPanelActionLink(Expression<Func<ControlPanelController, IActionResult>> actionExpression)
+		{
+			var memberSelectorExpression = (MethodCallExpression)actionExpression.Body;
+			var method = memberSelectorExpression.Method;
+
+			var controllerName = typeof(ControlPanelController).Name;
+
+			const string ControllerSuffix = nameof(Controller);
+			if (controllerName.EndsWith(ControllerSuffix, StringComparison.Ordinal))
+				controllerName = controllerName.Substring(0, controllerName.Length - ControllerSuffix.Length);
+
+			var actionName = method.Name;
+
+			return Tuple.Create<string, string?>(controllerName, actionName);
+		}
+
 		/// <summary>
 		/// Initializes a new instance of the <see cref="RootController"/> class.
 		/// </summary>
@@ -136,5 +158,19 @@ namespace Tgstation.Server.Host.Controllers
 
 			return (IActionResult?)this.TryServeFile(hostEnvironment, logger, $"{logoFileName}.svg") ?? NotFound();
 		}
+
+		/// <summary>
+		/// Workaround for the webpanel always expecting a trailing slash.
+		/// </summary>
+		/// <returns>A <see cref="RedirectResult"/> to the <see cref="ControlPanelController.GetChannelJson"/>.</returns>
+		[HttpGet(ControlPanelController.ChannelJsonRoute)]
+		public RedirectToActionResult WebpanelChannelRedirect()
+		{
+			var actionTuple = GetControlPanelActionLink(controller => controller.GetChannelJson());
+
+			return RedirectToActionPermanent(
+				actionTuple.Item2,
+				actionTuple.Item1);
+		}
 	}
 }

src/Tgstation.Server.Host/Core/Application.cs

@@ -1,4 +1,4 @@
-using System;
+using System;
 using System.Collections.Frozen;
 using System.Collections.Generic;
 using System.Globalization;
@@ -524,6 +524,7 @@ namespace Tgstation.Server.Host.Core
 					RequestPath = ControlPanelController.ControlPanelRoute,
 					EnableDefaultFiles = true,
 					EnableDirectoryBrowsing = false,
+					RedirectToAppendTrailingSlash = false,
 				});
 			}
 			else