Have 3 Options for Stock Availability in WooCommerce

If you want to have 3 options instead of 2 for stock availability such as, "In Stock", "Out of Stock" and "On Hold", use the following code within the functions.php file:

//** Have 3 Options for Stock Availability: In Stock, Out of Stock, and On Hold **//
function add_custom_stock_type() {
?>
<script type="text/javascript">
jQuery(function(){
jQuery('._stock_status_field').not('.custom-stock-status').remove();
});
</script>
<?php

woocommerce_wp_select( array( 'id' => '_stock_status', 'wrapper_class' => 'hide_if_variable custom-stock-status', 'label' => __( 'Stock status', 'woocommerce' ), 'options' => array(
'instock' => __( 'In stock', 'woocommerce' ),
'outofstock' => __( 'Out of stock', 'woocommerce' ),
'onhold' => __( 'On Hold', 'woocommerce' ), // The new option !!!
), 'desc_tip' => true, 'description' => __( 'Controls whether or not the product is listed as "in stock" or "out of stock" on the frontend.', 'woocommerce' ) ) );}
add_action('woocommerce_product_options_stock_status', 'add_custom_stock_type');

function save_custom_stock_status( $product_id ) {
update_post_meta( $product_id, '_stock_status', wc_clean( $_POST['_stock_status'] ) );
}
add_action('woocommerce_process_product_meta', 'save_custom_stock_status',99,1);

function woocommerce_get_custom_availability( $data, $product ) {
$stock_status = get_post_meta($product->id , '_stock_status' , true );
switch( $stock_status ) {
case 'onhold':
$data = array( 'availability' => __( 'On Hold', 'woocommerce' ), 'class' => 'on-hold' );
break;
case 'instock':
$data = array( 'availability' => __( 'Available Now', 'woocommerce' ), 'class' => 'in-stock' );
break;
case 'outofstock':
$data = array( 'availability' => __( 'Adopted', 'woocommerce' ), 'class' => 'out-of-stock' );
break;
}
return $data;
}
add_action('woocommerce_get_availability', 'woocommerce_get_custom_availability', 3, 2);