Merge branch '5.0'

* 5.0:
  [DI] Service locators can't be decorated
  [HttpClient] force HTTP/1.1 when NTLM auth is used
  [Validation][FrameworkBundle] Allow EnableAutoMapping to work without auto-mapping namespaces
  [Console][SymfonyQuestionHelper] Handle multibytes question choices keys and custom prompt
  [DI] fix auto-binding service providers to their service subscribers
  [Mailer] fixed undefined index when sending mail

Author: nicolas-grekas

Mailchimp/Transport/MandrillApiTransport.php

@@ -57,7 +57,8 @@ protected function doSendApi(SentMessage $sentMessage, Email $email, Envelope $e
             throw new HttpTransportException(sprintf('Unable to send an email (code %s).', $result['code']), $response);
         }
 
-        $sentMessage->setMessageId($result['_id']);
+        $firstRecipient = reset($result);
+        $sentMessage->setMessageId($firstRecipient['_id']);
 
         return $response;
     }

MandrillApiTransport.php

@@ -57,7 +57,8 @@ protected function doSendApi(SentMessage $sentMessage, Email $email, Envelope $e
             throw new HttpTransportException(sprintf('Unable to send an email (code %s).', $result['code']), $response);
         }
 
-        $sentMessage->setMessageId($result['_id']);
+        $firstRecipient = reset($result);
+        $sentMessage->setMessageId($firstRecipient['_id']);
 
         return $response;
     }