Merge branch '6.3' into 6.4

* 6.3:
  Add missing return type
  [HttpClient] Fix pausing responses before they start when using curl
  separate child and parent context in NotificationEmail on writes
  [Mailer] [Mailgun] Fix sender header encoding
  do not overwrite the cache key when it is false
  [Mailer] Throw TransportException when unable to read from socket
  [Serializer] Rewrite `AbstractObjectNormalizer::createChildContext()` to use the provided `cache_key` from original context when creating child contexts
  [HttpClient] Fix error chunk creation in passthru
  Adjusting and removing the 'review' attribute from the pt_br translation XML.
  [Serializer] Take unnamed variadic parameters into account when denormalizing
  Fix context data and display extra data

Author: nicolas-grekas

Tests/Transport/MailgunApiTransportTest.php

@@ -268,4 +268,17 @@ public function testTagAndMetadataHeaders()
         $this->assertArrayHasKey('v:Client-ID', $payload);
         $this->assertSame('12345', $payload['v:Client-ID']);
     }
+
+    public function testEnvelopeSenderHeaderIsCorrectlyEncoded()
+    {
+        $email = new Email();
+        $envelope = new Envelope(new Address('[email protected]', 'Žluťoučký Kůň'), [new Address('[email protected]')]);
+
+        $transport = new MailgunApiTransport('ACCESS_KEY', 'DOMAIN');
+        $method = new \ReflectionMethod(MailgunApiTransport::class, 'getPayload');
+        $payload = $method->invoke($transport, $email, $envelope);
+
+        $this->assertArrayHasKey('h:Sender', $payload);
+        $this->assertSame('=?utf-8?Q?=C5=BDlu=C5=A5ou=C4=8Dk=C3=BD_K=C5=AF=C5=88?= <[email protected]>', $payload['h:Sender']);
+    }
 }

Transport/MailgunApiTransport.php

@@ -87,7 +87,7 @@ protected function doSendApi(SentMessage $sentMessage, Email $email, Envelope $e
     private function getPayload(Email $email, Envelope $envelope): array
     {
         $headers = $email->getHeaders();
-        $headers->addHeader('h:Sender', $envelope->getSender()->toString());
+        $headers->addMailboxHeader('h:Sender', $envelope->getSender());
         $html = $email->getHtmlBody();
         if (null !== $html && \is_resource($html)) {
             if (stream_get_meta_data($html)['seekable'] ?? false) {