Create a webhook subscription using the url of this site with any path segment. For example:
https://web.prd-s5y-hook-receiver-c33e.prod.shopifyapps.com/my_unique_path
Trigger the webhook.
Visit the url from your webhook subscription. You should see your webhook.
How does this work?
The body of POST requests to any path segment are stored in a database. GET requests load all webhooks that have been received.
Who can create/read/delete webhooks on this site?
Anyone. All received webhooks are totally public and can be deleted by anyone.