Macro command

macro_rules! command {
    (
        $(#[$docs:meta])+
        $cmd:ident {
            command_type: $cmd_type:expr,
            command_class: $cmd_class:expr,
            command_index: $cmd_idx:expr,
            argument: $arg:ident,
            default_arg: $default_arg:expr,
            response_type: $res_type:expr,
        }
    ) => { ... };
}

Convenience macro to define a Command type.