Handle "all slashes" routes (#17596)

Author: kjac

src/Umbraco.Core/Routing/UriUtility.cs

@@ -111,6 +111,12 @@ public Uri UriToUmbraco(Uri uri)
         if (path != "/")
         {
             path = path.TrimEnd(Constants.CharArrays.ForwardSlash);
+
+            // perform fallback to root if the path was all slashes (i.e. https://some.where//////)
+            if (path == string.Empty)
+            {
+                path = "/";
+            }
         }
 
         return uri.Rewrite(path);

tests/Umbraco.Tests.UnitTests/Umbraco.Core/Routing/UriUtilityTests.cs

@@ -23,7 +23,9 @@ public class UriUtilityTests
 
     // test that the trailing slash goes but not on hostname
     [TestCase("http://LocalHost/", "http://localhost/")]
+    [TestCase("http://LocalHost/////", "http://localhost/")]
     [TestCase("http://LocalHost/Home/", "http://localhost/home")]
+    [TestCase("http://LocalHost/Home/////", "http://localhost/home")]
     [TestCase("http://LocalHost/Home/?x=y", "http://localhost/home?x=y")]
     [TestCase("http://LocalHost/Home/Sub1/", "http://localhost/home/sub1")]
     [TestCase("http://LocalHost/Home/Sub1/?x=y", "http://localhost/home/sub1?x=y")]