Performed review of "public intended" functionality provided in #1817

- Updated logic to take url from referrer rather than pass as a query parameter.
- Added tests to cover functionality.
- Updated 404 page with login action button if not signed in.
- Updated 404 page with text to indicate permissions may be affecting visibility.

Related to #1817 and #1706

app/Http/Controllers/Auth/LoginController.php

@@ -76,8 +76,9 @@ class LoginController extends Controller
             ]);
         }
 
-        if ($request->has('intended')) {
-            redirect()->setIntendedUrl($request->get('intended'));
+        $previous = url()->previous('');
+        if (setting('app-public') && $previous && $previous !== url('/login')) {
+            redirect()->setIntendedUrl($previous);
         }
 
         return view('auth.login', [