title: Rails 3 find_or_create by more than one attribute mongoid
body: <p>In this link <a href="https://stackoverflow.com/questions/3046607/rails-find-or-create-by-more-than-one-attribute">Rails find_or_create by more than one attribute?</a> can use more that one attribute with active record.</p>
  
  <p>How can I use more than attribute in mongoid?</p>
  
  <p>Thank you</p>