AutomateWoo Refer A Friend - Change referral coupon type to sign up fee percentage discount

functions.php

<?php

add_filter('automatewoo/referrals/coupon_data', 'my_automatewoo_referrals_custom_coupon_data' );

/**
 * @param array $coupon_data
 * @return array
 */
function my_automatewoo_referrals_custom_coupon_data( $coupon_data ) {
	$coupon_data['discount_type'] = 'sign_up_fee_percent';     
	return $coupon_data;
}