Proper error handling

[arthot]

SDK should throw a custom error with more fields to follow API error structure https://developers.evrythng.com/docs/http-verbs-and-error-codes#error-messages

Also e2e should include negative scenario testing

[C-D-Lewis]

It used to, but that doesn't work well with libraries and integrations that expect a native Error. So I used a misture of both - a native Error with a message you can parse as JSON. I think this is the right solution, unless you know an alternative that achieves both of these aims?