adjust to latest cs fixer rules

spec/Encoding/MemoryStream.php

@@ -103,7 +103,7 @@ public function getContents(): string
  return $this->read($this->size);
  }
 
- public function getMetadata(string $key = null)
+ public function getMetadata(?string $key = null)
  {
  $metadata = stream_get_meta_data($this->resource);
 

src/Authentication/Matching.php

@@ -27,7 +27,7 @@ final class Matching implements Authentication
  */
  private $matcher;
 
- public function __construct(Authentication $authentication, callable $matcher = null)
+ public function __construct(Authentication $authentication, ?callable $matcher = null)
  {
  if (is_null($matcher)) {
  $matcher = function () {

src/Cookie.php

@@ -73,7 +73,7 @@ public function __construct(
  $path = null,
  $secure = false,
  $httpOnly = false,
- \DateTime $expires = null
+ ?\DateTime $expires = null
  ) {
  $this->validateName($name);
  $this->validateValue($value);
@@ -109,7 +109,7 @@ public static function createWithoutValidation(
  $path = null,
  $secure = false,
  $httpOnly = false,
- \DateTime $expires = null
+ ?\DateTime $expires = null
  ) {
  $cookie = new self('name', null, null, $domain, $path, $secure, $httpOnly, $expires);
  $cookie->name = $name;
@@ -228,7 +228,7 @@ public function hasExpires()
  *
  * @return Cookie
  */
- public function withExpires(\DateTime $expires = null)
+ public function withExpires(?\DateTime $expires = null)
  {
  $new = clone $this;
  $new->expires = $expires;

src/Decorator/StreamDecorator.php

@@ -86,10 +86,7 @@ public function getContents(): string
  return $this->stream->getContents();
  }
 
- /**
- * @return mixed
- */
- public function getMetadata(string $key = null)
+ public function getMetadata(?string $key = null)
  {
  return $this->stream->getMetadata($key);
  }

src/Stream/BufferedStream.php

@@ -209,7 +209,7 @@ public function getContents(): string
  return $read;
  }
 
- public function getMetadata(string $key = null)
+ public function getMetadata(?string $key = null)
  {
  if (null === $this->resource) {
  if (null === $key) {