Improve error message logging when error response contain json

[andebor]

We currently treat all http error messages as strings when storing them. Several of the responses are actually json. This results in strings with escaped json. This doesn't have the best readability.
I suggest that we check the response for json before passing on the response. If it's json, we pass a long the object instead. (Might want to append i.e. the status code before passing it along.)

Instead of this:

{
  "id": "wpm78z4e45",
  "title": "TEST-owner-anders-dev-export",
  "start": "2023-03-08T15:29:59.092614+01:00",
  "end": "2023-03-08T15:30:01.080508+01:00",
  "lastError": "Received http sink error (401): {\"message\":\"code=400, message=missing or malformed jwt\"}\n"
}

Do something like this:

{
  "id": "wpm78z4e45",
  "title": "TEST-owner-anders-dev-export",
  "start": "2023-03-08T15:29:59.092614+01:00",
  "end": "2023-03-08T15:30:01.080508+01:00",
  "lastError": {
    "body": {
      "message": "code=400, message=missing or malformed jwt"
    },
    "title": "Received http sink error (401)",
    "statusCode": 401
  }
}

If the error doesn't contain json, it should use the old behavior.

[andebor]

I guess an option would be to do this on the client side. I'm not sure what we prefer.