Function emit 

pub fn emit<P, E>(
    channel: &E,
    kind: EventKind,
    payload: P,
) -> Result<(), AppError>
where
    P: Serialize + Clone,
    E: EventEmitter,

Emit an event through any EventEmitter channel.

This thin wrapper lets call sites omit the .emit(…) method chain and keeps the signature uniform across production and test code.