title: Redirect the user upon login based on user role in drupal 8
body: <p>In drupal 8 I have two separate roles admin and manager.</p>
  
  <p>If user logins with manager username and password, should be redirected to different page.</p>
  
  <p>We can use module but I need to do it through custom code in drupal 8.</p>
  
  <p>Please help me in the code to perform this condition in drupal 8 custom module.</p>