title: ObjectId in simpleSchema or collection2
body: <p>I am just playing around with meteor and started using simple-schema and collection2. I moved from mongoose and node so my question could be a bit noob, so bear with me.</p>
  
  <p>In mongoose I could just add a type called schema.ObjectId,in some field to emulate reference, but I don't see any such implication in collection2.
  Is there any quick solution for that?</p>
  
  <p>Is using type: String a good idea for this scenario?</p>
  
  <p>Thanks in advance</p>