`SignedPacket::from_packet` fails with CNAME + pubkey

[SeverinAlexB]

Bug Report

SignedPacket::from_packet fails to encode a cname that references the same public key that it is signed with. I am clueless why it does not work. The error message DnsError(InsufficientData) is not hinting to the problem at all.

called `Result::unwrap()` on an `Err` value: DnsError(InsufficientData)
stack backtrace:
   0: rust_begin_unwind
             at /rustc/82e1608dfa6e0b5569232559e3d385fea5a93112/library/std/src/panicking.rs:645:5
   1: core::panicking::panic_fmt
             at /rustc/82e1608dfa6e0b5569232559e3d385fea5a93112/library/core/src/panicking.rs:72:14
   2: core::result::unwrap_failed
             at /rustc/82e1608dfa6e0b5569232559e3d385fea5a93112/library/core/src/result.rs:1653:5
   3: core::result::Result<T,E>::unwrap
             at /rustc/82e1608dfa6e0b5569232559e3d385fea5a93112/library/core/src/result.rs:1077:23
   4: pknamescli::commands::pkarr::pkarr_records::tests::parse_spacefil2e
             at ./src/commands/pkarr/pkarr_records.rs:281:22
   5: pknamescli::commands::pkarr::pkarr_records::tests::parse_spacefil2e::{{closure}}
             at ./src/commands/pkarr/pkarr_records.rs:267:26
   6: core::ops::function::FnOnce::call_once
             at /rustc/82e1608dfa6e0b5569232559e3d385fea5a93112/library/core/src/ops/function.rs:250:5
   7: core::ops::function::FnOnce::call_once
             at /rustc/82e1608dfa6e0b5569232559e3d385fea5a93112/library/core/src/ops/function.rs:250:5

How to reproduce

#[cfg(test)]
mod tests {
    use pkarr::{dns::{rdata::RData, Name, Packet, ResourceRecord}, Keypair, SignedPacket};

    #[test]
    fn build_signed_packet_with_cname() {
        let keypair = Keypair::random();
        let pubkey = keypair.to_z32();
        let name = Name::new("www.pknames.p2p").unwrap();
        let data = format!("pknames.p2p.{pubkey}");
        let data = Name::new(&data).unwrap();
        let rdata = RData::CNAME(pkarr::dns::rdata::CNAME(data));
        let record = ResourceRecord::new(name, pkarr::dns::CLASS::IN, 5000, rdata);

        let mut packet = Packet::new_reply(0);
        packet.answers = vec![record];
        let signed = SignedPacket::from_packet(&keypair, &packet).unwrap();

    }
}

What to expect

Should parse as usual or maybe throw a better error message?