Zvt: Add nack packet/command

[minlux]

This PR adds a packet for the Nack (84 XX) command, to zvt.
This packet/command is somehow special, as it has not a fixed INSTR byte. Instead of INSTR the packets 2nd byte is the error code of the Nack.
The respective traits for serialization and deserialization are hand written, instead of generated using the Zvt macro, to deal with this speciality.

[dorezyuk]

puh I'm not sure - from what i see we would fall into

impl<T> ZvtSerializer for T
where
    Self: ZvtCommand
        + ZvtSerializerImpl<length::Adpu, encoding::Default, encoding::BigEndian>
        + ZvtSerializerImpl,
    encoding::Default: encoding::Encoding<Self>,
{
    fn zvt_serialize(&self) -> Vec<u8> {
        // Find a more elegant way to express this.
        let tag: Tag = encoding::BigEndian::decode(&[Self::CLASS, Self::INSTR])
            .unwrap()
            .0;
        <Self as ZvtSerializerImpl<length::Adpu, encoding::Default, encoding::BigEndian>>::serialize_tagged(self, Some(tag))
    }

    fn zvt_deserialize(bytes: &[u8]) -> ZVTResult<(Self, &[u8])> {
        let tag: Tag = encoding::BigEndian::decode(&[Self::CLASS, Self::INSTR])
            .unwrap()
            .0;
        <Self as ZvtSerializerImpl<length::Adpu, encoding::Default, encoding::BigEndian>>::deserialize_tagged(bytes, Some(tag))
    }
}
```... 

[dorezyuk]

i think I would to the following

pub struct Nack {
    error: u8
}

impl zvt_builder::encoding::Encoding<Nack> for zvt_builder::encoding::Default {
    fn decode(_bytes: &[u8]) -> zvt_builder::ZVTResult<(Nack, &[u8])> {
        Err(zvt_builder::ZVTError::NonImplemented)
    }

    fn encode(_input: &Nack) -> Vec<u8> {
        vec![]
    }
}

impl zvt_builder::ZvtSerializerImpl for Nack {
    fn serialize_tagged(&self, tag: Option<zvt_builder::Tag>) -> Vec<u8> {
        todo!()
    }

    fn deserialize_tagged(mut bytes: &[u8], tag: Option<zvt_builder::Tag>) -> zvt_builder::ZVTResult<(Self, &[u8])> {
        todo!()
    }
}

impl zvt_builder::ZvtSerializer for Nack {
    fn zvt_serialize(&self) -> Vec<u8> {
        // here goes the real impl
        todo!()
    }

    fn zvt_deserialize(bytes: &[u8]) -> zvt_builder::ZVTResult<(Self, &[u8])> {
        // here goes the real impl
        todo!()
    }
}

[minlux]

Do you want me to change the implementation as you proposed?
Or are you going to integrate it as you said?

[dorezyuk]

you do :)