Merge branch 'feature/canonical-redirect' into develop

Ensures that web requests are always redirected to the same casing as used in the topic graph. This helps ensure that there's alignment in the URL used in the browser, in the `SitemapController`, in the canonical URL, in search indexes, and in any reporting tools. In turn, that helps prevent issues with performance or reporting caused by some tools—such as Google Search Console or Google Analytics—interpreting two URLs that vary only by case as distinct URLs.

Author: JeremyCaney

OnTopic.AspNetCore.Mvc/ValidateTopicAttribute.cs

@@ -140,6 +140,18 @@ public override void OnActionExecuting(ActionExecutingContext filterContext) {
         return;
       }
 
+      /*------------------------------------------------------------------------------------------------------------------------
+      | Handle canonical URL
+      >-------------------------------------------------------------------------------------------------------------------------
+      | Most search engines are case sensitive, even though many web servers are configured case insensitive. To help avoid
+      | mismatches between the requested URL and the canonical URL, and to help ensure that references to topics maintain the
+      | same case as assigned in the topic graph, URLs that vary only by case will be redirected to the expected case.
+      \-----------------------------------------------------------------------------------------------------------------------*/
+      if (!currentTopic.GetWebPath().Equals(filterContext.HttpContext.Request.Path, StringComparison.Ordinal)) {
+        filterContext.Result = controller.RedirectPermanent(currentTopic.GetWebPath());
+        return;
+      }
+
       /*------------------------------------------------------------------------------------------------------------------------
       | Base processing
       \-----------------------------------------------------------------------------------------------------------------------*/