Function FromJSONObjectOptional

libs/cppjansson/cppjansson.hpp:189–198

template <typename T>
std::optional<T> FromJSONObjectOptional(json_t const * root, char const * field)
{
  auto * json = base::GetJSONOptionalField(root, field);
  if (!json)
    return {};

  std::optional<T> result{T{}};
  FromJSON(json, *result);
  return result;
}

template <typename T>
void FromJSONObjectOptionalField(json_t const * root, std::string const & field, T & result)