Change Details

I made `VoidTag` so i can use `std::optional<HandleVoid<ResultType>>` for any result. Probably the state of the optional can in the future be used do differentiate `done` and `canceled`.

I made `VoidTag` so i can use `std::optional<HandleVoid<ResultType>>` for any result. Another solution would be `std::optional<std::tuple<>>` for void results and `std::optional<std::tuple<ResultType>>` for non void results. There is no empty base class optimization anymore. Probably the state of the optional can in the future be used do differentiate `done` and `canceled`.

I made `VoidTag` so i can use `std::optional<HandleVoid<ResultType>>` for any result. Another solution would be `std::optional<std::tuple<>>` for void results and `std::optional<std::tuple<ResultType>>` for non void results. There is no empty base class optimization anymore. Probably the state of the optional can in the future be used do differentiate `done` and `canceled`.