fix: properly handle request errors

[LPkkjHD]

Currently when a request goes wrong (essentially when !response.ok) we always end up with some sort of Network Error, which is not the desired behavior when the spec and the generated typing expects us to have a <RequestSecifc>Error.

As this issue isn't new and has been solved in comments by SeanCondon as well as MarcusOhman91 already this is more of a paperwork PR.

Closes #188 Closes #113