Add credential handling instructions for Swagger UI (#2285)

Author: cay89

core/openapi.md

@@ -924,6 +924,32 @@ return [
 > **must** be set according to the
 > [OpenID Connect specification](https://openid.net/specs/openid-connect-core-1_0.html).
 
+## Sending Credentials with Swagger UI Requests
+
+When your API is deployed behind a proxy that uses cookie-based authentication (e.g. Cloudflare
+Access), Swagger UI's requests may be rejected because the authentication cookie is not forwarded by
+default. Enabling `withCredentials` adds a `requestInterceptor` to SwaggerUIBundle that sets
+`credentials: 'include'` on every outgoing request, ensuring cookies are sent alongside token and
+CORS requests.
+
+### Sending Credentials with Swagger UI Requests using Symfony
+
+> [!NOTE] This feature is only available with Laravel. You're welcome to contribute the Symfony
+> implementation [on GitHub](https://github.com/api-platform/core).
+
+### Sending Credentials with Swagger UI Requests using Laravel
+
+```php
+<?php
+// config/api-platform.php
+return [
+    // ...
+    'swagger_ui' => [
+        'with_credentials' => true,
+    ],
+];
+```
+
 ## Info Object
 
 The [info object](https://swagger.io/specification/#info-object) provides metadata about the API