Important: #109107 - Cache action endpoints should return JSON response

Description

AJAX endpoints registered as custom cache actions via \TYPO3\CMS\Backend\Backend\Event\ModifyClearCacheActionsEvent should return a JSON response containing success, title, and message fields.

The clear-cache toolbar now treats a missing or non-false success value as a successful operation and falls back to generic notification labels when title or message are absent. While this keeps older endpoints working without changes, providing explicit values gives users meaningful, context-specific feedback and ensures error conditions are surfaced correctly.

Hint

Update any custom cache action endpoint to return a structured JSON response:

use TYPO3\CMS\Core\Http\JsonResponse;

// Success
return new JsonResponse([
    'success' => true,
    'title'   => $languageService->sL('myext.locallang:notification.success.title'),
    'message' => $languageService->sL('myext.locallang:notification.success.message'),
]);

// Failure
return new JsonResponse([
    'success' => false,
    'title'   => $languageService->sL('myext.locallang:notification.error.title'),
    'message' => $languageService->sL('myext.locallang:notification.error.message'),
]);