AutomateWoo Refer A Friend - Make referral coupons use the user ID of the advocate instead of a random string

functions.php

<?php

// In addition to adding this code you should set the Coupon Expiry setting to zero to disable coupon expiry

add_filter('automatewoo/referrals/generate_advocate_key', 'my_automatewoo_referrals_generate_advocate_key', 10, 2 );

/**
 * @param $key
 * @param AW_Model_Referral_Advocate $advocate
 * @return int|string
 */
function my_automatewoo_referrals_generate_advocate_key( $key, $advocate ) {
	return $advocate->get_id();
}

Best I could come up with at this time is 'REF[user_id][first_name]': https://gist.github.com/jrick1229/cfd87548c66406a2492576b05fd93579
Using only first name creates advocate issues, as they are indistinguishable.