Resolve the "INTERMediator\FileMakerServer\RESTAPI\Supporting\CommunicationProvider::getOAuthIdentifier() never returns string so it can be removed from the return type" error detected by PHPStan

Author: matsuo

src/Supporting/CommunicationProvider.php

@@ -550,10 +550,10 @@ private function getSupportingProviders(): null|array
 
     /**
      * @param $provider
-     * @return string|array|null
+     * @return array|null
      * @ignore
      */
-    private function getOAuthIdentifier($provider): string|array|null
+    private function getOAuthIdentifier($provider): array|null
     {
         try {
             $this->callRestAPI(