Merge branch '6.4' into 7.0

* 6.4:
  stop marking parameters implicitly as nullable
  include message id provided by the MTA when dispatching the SentMessageEvent

Author: xabbuh

Tests/Fixtures/ServerRequest.php

@@ -26,10 +26,10 @@ class ServerRequest extends Message implements ServerRequestInterface
     public function __construct(
         string $version = '1.1',
         array $headers = [],
-        StreamInterface $body = null,
+        ?StreamInterface $body = null,
         private readonly string $requestTarget = '/',
         private readonly string $method = 'GET',
-        UriInterface|string $uri = null,
+        UriInterface|string|null $uri = null,
         private readonly array $server = [],
         private readonly array $cookies = [],
         private readonly array $query = [],