Get response json on failure

[einarmo]

In v1, some failure messages from the api has json data, which can contain useful information. This doesn't seem to be accessible in the current SDK. Ideally, ResponseException would give access to status code, message and response json if applicable.

[einarmo]

Seems like API error messages in v1 have a standard structure of
{ "code": xxx, "message": xxxxx ... various arrays }

arrays include "missing", "duplicated", "missingFields"...