Duplicate Webhook Subscription
Reuse the existing subscription, or register a different callback URL.
An HTTP 409 application/problem+json response:
{
"type": "https://problems.atlas.propertyfinder.com/webhooks-duplicate-subscription/",
"title": "Duplicate Webhook Subscription",
"status": 409,
"code": "webhooks_duplicate-subscription",
"detail": "A webhook subscription for this event type with the same callback URL already exists."
}