ざっくりRFC 9457

   POST /purchase HTTP/1.1
   Host: store.example.com
   Content-Type: application/json
   Accept: application/json, application/problem+json

   {
     "item": 123456,
     "quantity": 2
   }

   HTTP/1.1 403 Forbidden
   Content-Type: application/problem+json
   Content-Language: en

   {
    "type": "https://example.com/probs/out-of-credit",
    "title": "You do not have enough credit.",
    "detail": "Your current balance is 30, but that costs 50.",
    "instance": "/account/12345/msgs/abc",
    "balance": 30,
    "accounts": ["/account/12345",
                 "/account/67890"]
   }