migration symfony 5 4 (#300)

* symfony 5.4 (diff dev)

* symfony 5.4 (working)

* symfony 5.4 (update autoload)

* symfony 5.4 (remove swiftmailer mailer implementation)

* symfony 5.4 (php doc and split Global accessor class)


### Impacted packages:

composer require php:">=7.2.5 <8.0.0" symfony/console:5.4.* symfony/dotenv:5.4.* symfony/framework-bundle:5.4.* symfony/twig-bundle:5.4.* symfony/yaml:5.4.* --update-with-dependencies

composer require symfony/stopwatch:5.4.* symfony/web-profiler-bundle:5.4.* --dev --update-with-dependencies

lib/symfony/http-foundation/Session/Storage/Handler/NullSessionHandler.php

@@ -19,16 +19,18 @@ namespace Symfony\Component\HttpFoundation\Session\Storage\Handler;
 class NullSessionHandler extends AbstractSessionHandler
 {
     /**
-     * {@inheritdoc}
+     * @return bool
      */
+    #[\ReturnTypeWillChange]
     public function close()
     {
         return true;
     }
 
     /**
-     * {@inheritdoc}
+     * @return bool
      */
+    #[\ReturnTypeWillChange]
     public function validateId($sessionId)
     {
         return true;
@@ -37,14 +39,15 @@ class NullSessionHandler extends AbstractSessionHandler
     /**
      * {@inheritdoc}
      */
-    protected function doRead($sessionId)
+    protected function doRead(string $sessionId)
     {
         return '';
     }
 
     /**
-     * {@inheritdoc}
+     * @return bool
      */
+    #[\ReturnTypeWillChange]
     public function updateTimestamp($sessionId, $data)
     {
         return true;
@@ -53,7 +56,7 @@ class NullSessionHandler extends AbstractSessionHandler
     /**
      * {@inheritdoc}
      */
-    protected function doWrite($sessionId, $data)
+    protected function doWrite(string $sessionId, string $data)
     {
         return true;
     }
@@ -61,16 +64,17 @@ class NullSessionHandler extends AbstractSessionHandler
     /**
      * {@inheritdoc}
      */
-    protected function doDestroy($sessionId)
+    protected function doDestroy(string $sessionId)
     {
         return true;
     }
 
     /**
-     * @return bool
+     * @return int|false
      */
+    #[\ReturnTypeWillChange]
     public function gc($maxlifetime)
     {
-        return true;
+        return 0;
     }
 }