old_contents: var mongoose = require('mongoose');
  var Schema = mongoose.Schema;
  
  var userSchema = new Schema({}, { strict: false });
  
  module.exports = mongoose.model('User', userSchema);
  
new_contents: var mongoose = require('mongoose');
  var Schema = mongoose.Schema;
  
  var userSchema = new Schema({
    username: {
      type: String
    },
    email: {
      type: String
    },
    password: {
      type: String
    },
    hash: { // TODO make virtual
      type: String
    }
  });
  
  
  module.exports = mongoose.model('User', userSchema);
  
subject: Set mongoose schema for user.