This way we can capture the entire state of the error to determine.

Also worth doing: Including the entire error response in the returned object. This way, in cases like the 503 error in #2093 where the JSON payload isn't what our code expects. Things still work fine.

In that case, the 503 payload is

{
  "error": {
    "code": 503,
    "message": "Write collision, please retry.",
    "status": "UNAVAILABLE",
    "details": [
      {
        "@type": "type.googleapis.com/google.rpc.RetryInfo",
        "retryDelay": "1.000s"
      }
    ]
  }
}

This seems to be a JSON version of the google.rpc.status.Status protobuf message type, with an extra status field that looks like a google.rpc.code.Code.

Our error-payload-parsing code makes the assumption that the errors come in the form:

{
  "error": {
    "message": "...",
    "errors": [
        "..."
    ]
  },
  "...": "..."
}