Macro modern_subgroup_glue 

macro_rules! modern_subgroup_glue {
    (derived_length $name:ident, $feat:literal, $draft:ident) => { ... };
    (explicit_length $name:ident, $feat:literal, $draft:ident) => { ... };
}

Generates the conversion glue between one draft’s stateful SubgroupObjectReader and the draft-neutral object types.

Every draft from 14 on carries a typed ObjectStatus, so the leading keyword selects how the payload length reaches the wire instead: draft-14 derives it from the payload, while drafts 15-20 carry an explicit payload-length field, which this glue always sets from the payload.

Both arms funnel the draft-neutral AnySubgroupObject, whose status is a bare u64, through the target draft’s ObjectStatus::from_u64. That is the one place a status code the target draft does not assign can still be offered to an encoder at run time — relaying an object between drafts, for instance — and it is refused there with CodecError::InvalidField.