Method user_data

cpp/src/link.cpp:99–103

}

void link::user_data(void* user_data) const {
    pn_link_t* lnk = pn_object();
    link_context& lctx = link_context::get(lnk);
    lctx.user_data_ = user_data;
}

void* link::user_data() const {
    pn_link_t* lnk = pn_object();