Add is_string validation

Author: DominikWolos

src/Authenticator/RequestAuthenticator.php

@@ -44,7 +44,7 @@ public function authenticate(Request $request): bool
             $content = stream_get_contents($content);
         }
 
-        if (false === $content) {
+        if (!is_string($content)) {
             throw new \InvalidArgumentException('Invalid JSON payload', Response::HTTP_BAD_REQUEST);
         }
 

src/Controller/UserComAgreementsController.php

@@ -42,7 +42,7 @@ public function __invoke(Request $request): Response
                 $payload = stream_get_contents($payload);
             }
 
-            if (false === $payload) {
+            if (!is_string($payload)) {
                 return new JsonResponse('Invalid JSON payload', Response::HTTP_BAD_REQUEST);
             }