Merge branch '7.1' into 7.2

* 7.1:
  [HttpClient] Close gracefull when the server closes the connection abruptly
  ensure that tests are run with lowest supported Serializer versions
  read runtime config from composer.json in debug dotenv command

Command/DebugCommand.php

@@ -77,7 +77,19 @@ protected function execute(InputInterface $input, OutputInterface $output): int
             return 1;
         }
 
-        $filePath = $_SERVER['SYMFONY_DOTENV_PATH'] ?? $this->projectDirectory.\DIRECTORY_SEPARATOR.'.env';
+        if (!$filePath = $_SERVER['SYMFONY_DOTENV_PATH'] ?? null) {
+            $dotenvPath = $this->projectDirectory;
+
+            if (is_file($composerFile = $this->projectDirectory.'/composer.json')) {
+                $runtimeConfig = (json_decode(file_get_contents($composerFile), true))['extra']['runtime'] ?? [];
+
+                if (isset($runtimeConfig['dotenv_path'])) {
+                    $dotenvPath = $this->projectDirectory.'/'.$runtimeConfig['dotenv_path'];
+                }
+            }
+
+            $filePath = $dotenvPath.'/.env';
+        }
 
         $envFiles = $this->getEnvFiles($filePath);
         $availableFiles = array_filter($envFiles, 'is_file');