title: Room - only allow 1 item to have boolean set to true
body: <p>Using room with live data... one thing I can't figure out is this:</p>
  
  <pre><code>object1.isSelected == true;
  object2.isSelected == false;
  object3.isSelected == false;
  </code></pre>
  
  <p>if I set 'isSelected' to true on object3, I want it to become false in object 1. </p>
  
  <p><strong>Is there a way to do this without observing both objects, making the switch, and then updating both objects?</strong></p>