Remove hard-coded path to wp-content

Can you please update the code, so paths to your plugin are no longer hard-coded.
Use something like wp_enqueue_script('bpost-custom-script', plugins_url('assets/js/bpost-export-message.js', dirname(__FILE__, 2)), array('jquery'), null, true);

See https://roots.io/wordpress-plugins-that-assume-your-directory-structure/