Derive Macro EventPayload 

#[derive(EventPayload)]
{
    // Attributes available to this derive:
    #[batpak]
}

Derives batpak::event::EventPayload for a named-field struct.

Requires #[batpak(category = N, type_id = N)] on the struct. See batpak::event::EventPayload and ADR-0010 for the full contract.