Rename UI controllers

BTCPayServer/Controllers/UIErrorController.cs

@@ -0,0 +1,28 @@
+using System;
+using System.Linq;
+using Microsoft.AspNetCore.Mvc;
+
+namespace BTCPayServer.Controllers
+{
+    public class UIErrorController : Controller
+    {
+        [Route("/errors/{statusCode:int}")]
+        public IActionResult Handle(int? statusCode = null)
+        {
+            if (Request.Headers.TryGetValue("Accept", out var v) && v.Any(v => v.Contains("text/html", StringComparison.OrdinalIgnoreCase)))
+            {
+                if (statusCode.HasValue)
+                {
+                    var specialPages = new[] { 404, 406, 417, 429, 500, 502, 403 };
+                    if (specialPages.Any(a => a == statusCode.Value))
+                    {
+                        var viewName = statusCode.ToString();
+                        return View(viewName);
+                    }
+                }
+                return View(statusCode);
+            }
+            return this.StatusCode(statusCode.Value);
+        }
+    }
+}