title: How to modify default filter logic of mat-table to only filter for visible table values
body: <p>I am using a mat-table and the default filter seems to also search for fields that are not visible but exist in my dataSource object.</p>
  
  <p>My Object consists of following properties:</p>
  
  <ul>
  <li>Id: string </li>
  <li>description: string </li>
  <li>srcStep: string </li>
  <li>dstStep: string</li>
  </ul>
  
  <p>Applying 
  <code>this.dataSource.filterPredicate = (data: MyDataSource, filter: string) =&gt; data.description.trim().toLowerCase().indexOf(filter) != -1;</code>
  seems to work fine for one column.</p>
  
  <p>How can I modify filterPredicate to also check for srcStep but not for dstStep</p>