title: How to add required asterisk in a custom control?
body: <p>I'm using angular 6 to create a custom component which contains a custom form control. So far, I've implemented <code>ControlValueAccessor</code> in my component.</p>
  
  <p>My custom control is a simple <code>MatSelect</code> component from Angular Material. I want to show the asterisk (<code>*</code>) for when that control is required.</p>
  
  <p>So far, I've got the custom control to work, but adding the <code>required</code> attribute to the component doesn't add the asterisk to my control!</p>
  
  <pre class="lang-html prettyprint-override"><code>&lt;app-provinces formControlName="projectProvince" required&gt;&lt;/app-provinces&gt;
  </code></pre>
  
  <p>Should I define an <code>@Input</code> variable for it and handle it manually, or should it be done automatically?</p>