old_contents: var mongoose = require('mongoose'),
    Schema = mongoose.Schema;
  
  var user = new Schema({
    _id: String,
    name: String,
    email: String,
    office: String,
    phone: String,
    mobile: String,
    roles: [String],
    lastVisitedOn: Date,
    forms: [String],
    travelers: [String],
    subscribe: {
      type: Boolean,
      default: false
    }
  });
  
  var User = mongoose.model('User', user);
  module.exports = {
    User: User
  };
new_contents: var mongoose = require('mongoose'),
    Schema = mongoose.Schema,
    ObjectId = Schema.Types.ObjectId;
  
  var user = new Schema({
    _id: String,
    name: String,
    email: String,
    office: String,
    phone: String,
    mobile: String,
    roles: [String],
    lastVisitedOn: Date,
    forms: [ObjectId],
    travelers: [ObjectId],
    subscribe: {
      type: Boolean,
      default: false
    }
  });
  
  var User = mongoose.model('User', user);
  module.exports = {
    User: User
  };
subject: update user model to use objectid