title: Can we define property of Mongoose schema model as another model
body: <p>I was creating models for my application using mongoose,
  Basically when creating 2 models like this.</p>
  
  <pre><code>// user.js
  
  var mongoose = require('mongoose');
  var Schema = mongoose.Schema;
  
  var user = new Schema({
    $key: String,
  
    us_first: String,
    us_family: String,
    displayName: String,
    email: String,
  });
  
  module.exports = mongoose.model('user', user);
  
  
  
  // project.js
  var mongoose = require('mongoose');
  var Schema = mongoose.Schema;
  
  var project = new Schema({
    $key: String,
    project_creator: String,
  
  });
  
  module.exports = mongoose.model('project', project);
  </code></pre>
  
  <p>Now what i want is in the <code>project</code> model, the type of <code>project_creator</code> should be the <code>user</code> model ( right now its just a string type ).</p>
  
  <p>I'm asking this because when i doing frontend using Angular and Typescript, i can declare the project model as something like this :</p>
  
  <pre><code>// user.ts
  export class User {
      $key: string;    
      us_first: string;
      us_family: string;
      displayName: string;
      email: string;
  
  // project.ts
  export class Project {
    $key: string;
    project_creator: User;
  </code></pre>
  
  <p>So i wonder if I can declare the samething in mongoose </p>