All URLs are validated via a simple token exchange mechanism in order for Shippie to trust that you control the target server.
This happens exactly at webhook creation from the Shippie dashboard, Shippie will issue a GET request to your webhook URL with a query string of check=<random_string>.
Your webhook server should respond back with the <random_string> in order for validation to succeed.
Example:
https://yourwebsite.com/webhooks?check=example
app.get("/webhooks", (req, res) => {
res.status(200).send(req.query.check)
})// true, req.query.check send it back
reply = request.GET.get('check')
#send example and reply back with 200
$reply_value = $_GET['check']; // Outputs example and then send it back