Customer Account Number for WooCommerce - woocommerce

Question

In WooCommerce, from "Adding a hidden fields to checkout and process it through order" answer thread, which generates a verification number on checkout for orders,
I am trying to figure out how to turn this into a account number instead by which I mean:
when the customer registers, a unique number is generated
that number is saved to the account
the number can be displayed used echo later on
This is what I have tried so far (without success) =>
OPTION 1:
add_action( 'woocommerce_register_form_start', 'user_account_nr' );
function user_account_nr() {
$billing_account_number = '';
if ( isset( $_POST['billing_account_number'] ) ) {
$billing_account_number = $_POST['billing_account_number'];
}
?>
<p class="form-row form-row-first">
<input type="hidden" class="input-hidden" name="billing_account_number" id="reg_billing_account_number" value="<?php if ( ! empty( $_POST['billing_account_number'] ) ) esc_attr_e( $billing_account_number ); ?>" />
</p>
<div class="clear"></div>
<?php
}
add_action('woocommerce_created_customer', 'add_account_number');
function add_account_number($user_id)
{
$accountnumber = wp_rand(10000,99999);
update_user_meta($user_id, 'billing_account_number', $accountnumber);
}
OPTION 2:
add_action('user_register','aacount_on_user_register');
function account_on_user_register($user_id){
$last_name = $_POST['last_name'];
if ( isset($last_name) ){
$account_id = wp_rand(10000,99999) . $user_id;
add_user_meta( $user_id, 'account_id', $account_id);
}
}
/* Add user "account_id" meta when user registers */
add_action('woocommerce_created_customer', 'admin_email_on_registration', 10 , 1);
function admin_email_on_registration($user_id) {
$user = wp_get_current_user();
$last_name = $user->last_name;
if ( isset($last_name) ){
$account_id = wp_rand(10000,99999) . $user_id;
add_user_meta( $user_id, 'account_id', $account_id);
}
}
Here is a third option I was trying to make work:
function uuid() {
return sprintf('%04x%04x-%04x-%04x-%04x-%04x%04x%04x',
mt_rand(0, 0xffff), mt_rand(0, 0xffff),
mt_rand(0, 0xffff),
mt_rand(0, 0x0fff) | 0x4000,
mt_rand(0, 0x3fff) | 0x8000,
mt_rand(0, 0xffff), mt_rand(0, 0xffff), mt_rand(0, 0xffff)
);
}
add_action('woocommerce_created_customer', 'generate_unique_id_after_user_created', 10, 3);
function generate_unique_id_after_user_created( $user_id, $form_id,$sub_id ) {
if( !empty( $user_id ) ) {
$user_data = array(
'ID' => $user_id,
'user_login' => uuid(),
'user_email' => '',
);
$updated_user_id = wp_update_user( $user_data );
if ( is_wp_error( $updated_user_id ) ) {
// There was an error, probably that user doesn't exist.
} else {
// Success!
}
}
}