Feature: #107436 - Symfony Translation Component Integration

Description

TYPO3 now utilizes the Symfony Translation component for reading localization label files - such as XLIFF and PO - instead of its custom localization parsers.

The migration brings several improvements:

Standardized file parsing using Symfony's translation loaders
Enhanced API for accessing translation catalogues
Support for custom translation loaders following Symfony standards

The new system maintains backward compatibility while providing a modern foundation for future improvements with translatable labels.

In addition, all label-related configuration options have been streamlined under the $GLOBALS['TYPO3_CONF_VARS']['LANG'] namespace.

The following new configuration options have been introduced:

$GLOBALS['TYPO3_CONF_VARS']['LANG']['loader'] - Configure custom translation loaders
$GLOBALS['TYPO3_CONF_VARS']['LANG']['requireApprovedLocalizations'] - Moved from SYS.lang
$GLOBALS['TYPO3_CONF_VARS']['LANG']['format'] - Moved from SYS.lang
$GLOBALS['TYPO3_CONF_VARS']['LANG']['availableLocales'] - Moved from EXTCONF.lang
$GLOBALS['TYPO3_CONF_VARS']['LANG']['resourceOverrides'] - Moved from SYS.locallangXMLOverride

Custom Translation Loaders

Extension developers can now implement custom translation loaders by implementing Symfony's translation loader interfaces:

use Symfony\Component\Translation\Loader\LoaderInterface;
use Symfony\Component\Translation\MessageCatalogue;

class CustomLoader implements LoaderInterface
{
    public function load(mixed $resource, string $locale, string $domain = 'messages'): MessageCatalogue
    {
        // Custom loading logic
        $catalogue = new MessageCatalogue($locale);
        // ... populate catalogue
        return $catalogue;
    }
}

Register custom loaders via configuration:

$GLOBALS['TYPO3_CONF_VARS']['LANG']['loader']['fileEnding'] = \MyExtension\Translation\CustomLoader::class;

Impact

All previous configuration options have been moved to the new $GLOBALS['TYPO3_CONF_VARS']['LANG'] namespace, these are automatically migrated to the new location when accessing the install tool.

Please note: This functionality only affects internal handling of translation files ("locallang" files). The public API of the localization system remains unchanged.