message: Validate the token in NEW_TOKEN frames is not empty
diff: // SPDX-License-Identifier: Apache-2.0
  use crate::{frame::Tag, varint::VarInt};
  -use s2n_codec::{decoder_parameterized_value, Encoder, EncoderValue};
  +use s2n_codec::{decoder_invariant, decoder_parameterized_value, Encoder, EncoderValue};
  //= https://tools.ietf.org/id/draft-ietf-quic-transport-32.txt#19.7
  //# A server sends a NEW_TOKEN frame (type=0x07) to provide the client
  @@ -51,6 +51,12 @@ decoder_parameterized_value!(
  let (token, buffer) = buffer.decode_slice_with_len_prefix::<VarInt>()?;
  let token = token.into_less_safe_slice();
  + //= https://www.rfc-editor.org/rfc/rfc9000.txt#19.7
  + //# A client MUST treat receipt of a NEW_TOKEN frame
  + //# with an empty Token field as a connection error
  + //# of type FRAME_ENCODING_ERROR.
  + decoder_invariant!(!token.is_empty(), "empty Token field");
  +
  let frame = NewToken { token };
  Ok((frame, buffer))
  