Redirect to url with trailing slash, WITHOUT the protocol and host.

Crow does not know the correct protocol when behind a reverse proxy.
So instead, simply redirect to the same url and add a trailing slash.

include/crow/routing.h

@@ -1462,16 +1462,7 @@ namespace crow // NOTE: Already documented in "crow/app.h"
             {
                 CROW_LOG_INFO << "Redirecting to a url with trailing slash: " << req.url;
                 res = response(301);
-
-                // TODO(ipkn) absolute url building
-                if (req.get_header_value("Host").empty())
-                {
-                    res.add_header("Location", req.url + "/");
-                }
-                else
-                {
-                    res.add_header("Location", (using_ssl ? "https://" : "http://") + req.get_header_value("Host") + req.url + "/");
-                }
+                res.add_header("Location", req.url + "/");
                 res.end();
                 return;
             }