Feature: #97595 - Provide default queue for notifications 

See forge#97595

Description 

To allow dispatching notifications to the user the easy way, a new global flash message queue, identified by TYPO3\CMS\Core\Messaging\FlashMessageQueue::NOTIFICATION_QUEUE, is introduced that takes the flash message and renders it as a notification on the top-right edge of the backend.

Backend modules based on \TYPO3\CMS\Backend\Template\ModuleTemplate automatically gain advantage of this feature.

Example 

$flashMessageService = GeneralUtility::makeInstance(FlashMessageService::class);
$notificationQueue = $flashMessageService->getMessageQueueByIdentifier(
    FlashMessageQueue::NOTIFICATION_QUEUE
);
$flashMessage = GeneralUtility::makeInstance(
    FlashMessage::class,
    'I\'m a message rendered as notification',
    'Hooray!',
    FlashMessage::OK
);
$notificationQueue->enqueue($flashMessage);
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Impact 

All flash messages dispatched to the flash message queue FlashMessageQueue::NOTIFICATION_QUEUE will be rendered as notifications in the browser.