bool operator()(const UserName &u1, const UserName &u2) const {
if(u1.user()==u2.user() && u1.email()==u2.email()) return true;
return false;
}
size_t operator()(const UserName &u) const {
return std::hash<std::string>()(u.user()) ^ std::hash<std::string>()(u.email());
}