Issue #3321924: Keycloak locale param can be a problem for multilingual URIs

src/EventSubscriber/KeycloakRequestSubscriber.php

@@ -124,7 +124,8 @@ class KeycloakRequestSubscriber implements EventSubscriberInterface {
       }
       // Add parameter to request query, so the Keycloak login/register
       // pages will load using the right locale.
-      $query['kc_locale'] = $langcode;
+      $locale_param = $this->keycloak->getLocale();
+      $query[$locale_param] = $langcode;
     }
 
     // Generate the endpoint URL including parameters.