Duplicate Reference
Use a unique reference, or update the existing listing instead.
An HTTP 422 application/problem+json response:
{
"type": "https://problems.atlas.propertyfinder.com/listings-duplicate-reference/",
"title": "Duplicate Reference",
"status": 422,
"code": "listings_duplicate-reference",
"detail": "A listing with this reference already exists for your client account."
}