params_view() = default;

constexpr
params_view(params_view const& other) = default;

params_view(
    params_view const& other,
    encoding_opts opt) noexcept;

params_view(core::string_view s);

params_view(
    core::string_view s,
    encoding_opts opt);

params_view qp;

return params_view( "" );