HandleUntypedError should be called in the default case of errors in the handlers after all recognised have been handled.

NewApiError is a reimplementation of the default huma.NewErrorWithContext and allows ApiError to be used as the default over huma.ErrorModel.

ApiError is a subset of the default huma.ErrorModel with both the status and title stripped out from the final response as they can be inferred from the header and are redundant.