PHP version incompatibility with openssl_decrypt

[nabilanam]

The openssl_decrypt tag parameter was added in PHP 7.1.
Because of that PHP 7.0 gives error saying it accepts 5 parameters.
I think composer.json PHP versions need to be updated.

lib-webtopay/src/WebToPay/Util.php

Lines 49 to 56 in ea83971

	$decryptedText = openssl_decrypt(
	$ciphertext,
	self::GCM_CIPHER,
	$key,
	OPENSSL_RAW_DATA,
	$iv,
	$tag
	);

Documentation: https://www.php.net/manual/en/function.openssl-decrypt.php#refsect1-function.openssl-decrypt-parameters