JSon response not detected with header containing utf8

src/Client.php

@@ -13,6 +13,7 @@
 use Joomla\Http\Exception\UnexpectedResponseException;
 use Joomla\Http\Http;
 use Joomla\Http\HttpFactory;
+use Joomla\Http\Response;
 use Joomla\Input\Input;
 use Joomla\Uri\Uri;
 
@@ -79,6 +80,24 @@ public function __construct($options = [], ?Http $http = null, ?Input $input = n
         $this->application = $application;
     }
 
+    /**
+     * Tests if given response contains JSON header
+     *
+     * @param Response  $response The response object
+     *
+     * @return  boolean
+     *
+     */
+    protected function isJsonResponse(Response $response)
+    {
+        foreach ($response->getHeader('Content-Type') as $type) {
+            if (str_starts_with($type, 'application/json')) {
+                return true;
+            }
+        }
+        return false;
+    }
+
     /**
      * Get the access token or redirect to the authentication URL.
      *
@@ -114,7 +133,7 @@ public function authenticate()
                 );
             }
 
-            if (in_array('application/json', $response->getHeader('Content-Type'))) {
+            if ($this->isJsonResponse($response)) {
                 $token = array_merge(json_decode((string) $response->getBody(), true), ['created' => time()]);
             } else {
                 parse_str((string) $response->getBody(), $token);
@@ -388,7 +407,8 @@ public function refreshToken($token = null)
             );
         }
 
-        if (in_array('application/json', $response->getHeader('Content-Type'))) {
+
+        if ($this->isJsonResponse($response)) {
             $token = array_merge(json_decode((string) $response->getBody(), true), ['created' => time()]);
         } else {
             parse_str((string) $response->getBody(), $token);