chore: upgrade to laravel 7 (#3746)

app/Http/Controllers/Api/Auth/OAuthController.php

@@ -16,6 +16,7 @@ use Illuminate\Support\Facades\Redirect;
 use Barryvdh\Debugbar\Facade as Debugbar;
 use Illuminate\Support\Facades\Validator;
 use Illuminate\Contracts\Encryption\Encrypter;
+use Symfony\Component\HttpFoundation\Response;
 
 class OAuthController extends Controller
 {
@@ -60,9 +61,9 @@ class OAuthController extends Controller
      * Log in a user and returns an accessToken.
      *
      * @param Request $request
-     * @return \Symfony\Component\HttpFoundation\Response
+     * @return \Symfony\Component\HttpFoundation\Response|null
      */
-    public function login(Request $request)
+    public function login(Request $request): ?Response
     {
         $isvalid = $this->validateRequest($request);
         if ($isvalid !== true) {
@@ -87,7 +88,7 @@ class OAuthController extends Controller
             return Route::respondWithRoute('oauth.verify');
         }
 
-        return;
+        return null;
     }
 
     /**