title: MongoDB/Mongoose: Updating entire document with findOneAndUpdate()
body: <p>I want to use the <code>findOneAndUpdate()</code> method to either create a document if it doesn't exist, or update it if does exist. Consider the following code:</p>
  <pre><code>SampleComment = new Comment({
      id: '00000001',
      name: 'My Sample Comment',
      ...
  })
  </code></pre>
  <p>This is my attempt to find out if <code>SampleComment</code> aldready exists, and if so, update it, otherwise creating it:</p>
  <pre><code>Comment.findOneAndUpdate(
      { id: SampleComment.id }, 
      { SampleComment }, // &lt;- NOT PASSING THE OBJECT
      { upsert: true, setDefaultsOnInsert: true }, 
      function(error, result) {
          ...
  });
  </code></pre>
  <p>I'm trying to pass the Model-instance as an object in the second argument, but result is only returning the default values of the model. Same goes for the document itself.</p>
  <p>How do I pass the entire object <code>SampleComment</code> correctly in the second argument?</p>