Add examples with custom HTTP exceptions

[Fcmam5]

Add an example of how to achieve the following:

   {
    "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"]
   }

src: https://datatracker.ietf.org/doc/html/rfc7807#page-3

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A use case where the application throws a business-specific exception