Function usage_from_view

src/config.cpp:217–228

    template<class T>
    ::std::optional<int> usage_from_view(const ::std::string_view &usage, const ::std::optional<int>(&original)) {
#define _CONVERT_(x) \
  if (usage == #x##sv) \
  return (int) T::x
      _CONVERT_(lowlatency);
      _CONVERT_(lowlatency_high_quality);
      _CONVERT_(transcoding);
      _CONVERT_(ultralowlatency);
      _CONVERT_(webcam);
#undef _CONVERT_
      return original;
    }

    int coder_from_view(const ::std::string_view &coder) {
      if (coder == "auto"sv) {