Only include non-400-like errors in ApiError

[KodrAus]

I don't think there's a lot of value including errors like ActionRequestValidation or Parsing in ApiError. It's really meant to be a structure that you can easily programmatically match on and respond to. But there isn't really much you can do with parsing errors.

We have this distinction between 'errors you can deal with' and errors you can log and fail with' in elastic`, so we should do the same here and capture other errors from the API elsewhere.

[KodrAus]

A bit of a papercut with the API response as it is is that it doesn't capture backtraces like client errors. I want the error to be easily matchable in a result, but this is kind of unfortunate.