 
   addUser = (users, user, owner)->
 
-    newUsers = removeUser users, user
     newUsers.push { id: user.getId(), owner }
+    newUsers = excludeUser users, user
 
     return newUsers
 

    return owner


  removeUser = (users, user)->

    userId   = user.getId()
    newUsers = []

    users = @users.splice 0

    for user in usersToRemove
      users = excludeUser users, user

    @update $set: { users }, callback

