src/Helper/ChecksumHelper.php
public static function generateChecksum2(int $orderId, string $sharedKey, int $currency): string
    {
        return strtolower(md5($orderId.'+'.$sharedKey.'+'.$currency));
    }
public static function generateChecksum2(int $orderId, string $sharedKey, int $currency): string
    {
        return strtolower(md5($orderId.'+'.$sharedKey.'+'.$currency));
    }
Dandomain has a bug in their payment implementation where they don't
include amount in checksum on their complete/success page.
That is why we have a second method for computing that checksum.

@param int    $orderId
@param string $sharedKey
@param int    $currency

@return string