title: How does nestjs pubsub.publish serializes the object?
body: <p>I'm using:nestjs, graphql(with subscription), mongodb,typegoose.
  When I try to use a scalable graphql subscription, I chose to use the lib <strong>graphql-redis-subscription</strong>. The problem is here:</p>
  <h3>When I use built-in pubsub</h3>
  built-in
  <pre><code>pubsub.publish('name':{name: mongodbObject})
  </code></pre>
  <p>This mongodbObject returned will automatically add an <code>id</code> field (string for _id) whenever I need it. I guess this has something to do with pubsub serializer or my app serializer pipe.</p>
  redisPubSub
  <pre><code>redisPubSub.publish('name':{name: mongodbObject})
  </code></pre>
  <p>This mongodbObject will not return <code>id</code>, which makes my front end throw errors. But it does provide a serializer option to change the way it works.</p>
  <h3>How to get the serializer of nestjs-graphql-subscription?</h3>