Return error on unknown object key

[bramp]

I would like the gojay codegen tool to have a flag to return a error if an unknown field is encountered.

For example

func (m *Message) UnmarshalJSONObject(dec *gojay.Decoder, k string) error {
	switch k {
	case "type":
		return dec.String(&m.Type)

	case "message":
		return dec.String(&m.Message)

        /////// New code
        default:
		return errUnknownField
	}
	//////
}