Merge branch '4.1'

* 4.1:
  [DependencyInjection] Fix tags on multiple decorated service
  fix merge
  SCA: reverted code style changes
  SCA: reverted code style changes
  SCA: applied requested code style changes
  SCA: simplify some ifs in favour of null coalescing operator

Author: nicolas-grekas

DependencyInjection/SecurityExtension.php

@@ -312,11 +312,7 @@ private function createFirewall(ContainerBuilder $container, $id, $firewall, &$a
         $contextKey = null;
         // Context serializer listener
         if (false === $firewall['stateless']) {
-            $contextKey = $id;
-            if (isset($firewall['context'])) {
-                $contextKey = $firewall['context'];
-            }
-
+            $contextKey = $firewall['context'] ?? $id;
             $listeners[] = new Reference($this->createContextListener($container, $contextKey));
             $sessionStrategyId = 'security.authentication.session_strategy';
         } else {