Function build_operation_context_attrs 

pub fn build_operation_context_attrs(
    endpoint: Option<String>,
    adverb: Option<&'static str>,
) -> Attrs

Build an Attrs carrier populated with the operation-context keys an endpoint-send site wants to stamp onto its outgoing request.

Callers supply the values they know in scope at the send site (qualified endpoint name, adverb token). Any None is simply omitted — the marker-driven stamp filters on presence.