[TFuture](API\Runtime\Core\Async\TFuture)< [FConcertDataStoreResult](API\Plugins\ConcertSyncCore\FConcertDataStoreResult) > InternalFetchOrAdd ( const [FName](API\Runtime\Core\UObject\FName) & Key, const [UScriptStruct](API\Runtime\CoreUObject\UObject\UScriptStruct) * Type, const [FName](API\Runtime\Core\UObject\FName) & TypeName, const void * Payload )