Function strings

test/generator_test.cpp:150–158

// reference = std::string_view
template<typename Allocator>
co_context::generator<std::string_view, std::string>
strings(std::allocator_arg_t, Allocator) {
    co_yield {};
    co_yield "start";
    for (auto sv : string_views()) {
        co_yield std::string{sv} + '!';
    }
    co_yield "end";
}

// Resulting vector is deduced using ::value_type.
template<std::ranges::input_range R>