Send custom notification on order status page - with payment link

Custom-notification.php

<?php
add_action("woocommerce_order_status_changed", "my_notification");

function my_notification($order_id) {
   global $woocommerce;
   $order = new WC_Order( $order_id );
   
   // Set you own custom order status here
   // NOTE - payment link only works for pending or unpaid orders
   if($order->status === 'pending' ) {
      
      //Generate a payment URL
      $payment_page = $order->get_checkout_payment_url();

      // Create a mailer
      $mailer = $woocommerce->mailer();

      $message_body = __( 'My message to the shopper with payment <a href="'.$payment_page.'">link</a>' );

      $message = $mailer->wrap_message(
      // Message head and message body.
      sprintf( __( 'Order %s received' ), $order->get_order_number() ), $message_body );

      // Send email
      $mailer->send( $order->billing_email, sprintf( __( 'Order %s received' ), $order->get_order_number() ), $message );

      // Set status to pending payment (if you are using a custom staus above)
      $order->update_status('pending');
     }
}
?>