Fix: Deprecation warning in PHP 8.4 (#416)

* Fixed deprecation warning in PHP 8.4 about implicitly marking a parameter as null instead of typing it explicitly

* Fixed a few more deprecation warnings in PHP 8.4

Author: marshallthornton

src/Contracts/ApiHelper.php

@@ -24,7 +24,7 @@ interface ApiHelper
      *
      * @return self
      */
-    public function make(Session $session = null);
+    public function make(?Session $session = null);
 
     /**
      * Set an existing API instance.

src/Services/ApiHelper.php

@@ -39,7 +39,7 @@ class ApiHelper implements IApiHelper
     /**
      * {@inheritdoc}
      */
-    public function make(Session $session = null): self
+    public function make(?Session $session = null): self
     {
         // Create the options
         $opts = new Options();
@@ -517,7 +517,7 @@ protected function chargeApiPath(ChargeType $chargeType): string
      *
      * @return array
      */
-    protected function doRequest(ApiMethod $method, string $path, array $payload = null)
+    protected function doRequest(ApiMethod $method, string $path, ?array $payload = null)
     {
         $response = $this->api->rest($method->toNative(), $path, $payload);
         if ($response['errors'] === true) {
@@ -563,7 +563,7 @@ protected function doRequestGraphQL(string $query, array $payload = []): array
      *
      * @return NullableShopDomain
      */
-    private function getShopDomain(Session $session = null): NullableShopDomain
+    private function getShopDomain(?Session $session = null): NullableShopDomain
     {
         // Check for existing session passed in
         if ($session && $session->getShop()) {

src/Util.php

@@ -65,7 +65,7 @@ public static function createHmac(array $opts, string $secret): Hmac
      *
      * @return mixed
      */
-    public static function parseQueryString(string $queryString, string $delimiter = null): array
+    public static function parseQueryString(string $queryString, ?string $delimiter = null): array
     {
         $commonSeparator = [';' => '/[;]\s*/', ';,' => '/[;,]\s*/', '&' => '/[&]\s*/'];
         $defaultSeparator = '/[&;]\s*/';