title: ngrx entities adapter addAll and nested state
body: <p>I have a scenario where I have a list of users on a users page. Each user has his own list of apps, and when a user is clicked, the corresponding list of apps is displayed. I would like to use the ngrx entity adapter, but first I need to design my state. One option is this:</p>
  
  <pre><code>const state = {
     usersState: {
        entities: {},
        apps: {
           entities: {}
        }
     }
  }
  </code></pre>
  
  <p>And the other is this:</p>
  
  <pre><code>const state = {
     usersState: {
        entities: {},
     },
     appsState: {
        entities: {}
     }
  }
  </code></pre>
  
  <p>Since there are no apps outside the users page, the first option makes more sense to me, but with that approach I have a problem: how do I use the <code>addAll</code>  method of the adapter? As far as I understand, and correct me if I'm wrong, <code>addAll</code> accepts a payload that represents a list of items as first parameter, the state as second parameter and somehow merges them together. Can you show an example how to use the adapter to update the nested state? Or maybe the solution is to go for the second option? Thanks.</p>