title: How to set default timestamp to now() + n days?
body: <p>I am developing an auth flow, where tokens with expiry timestamp are used. 
  When a user logs in successfully, a token is generated and saved in the DB. </p>
  
  <p>I know I can add <code>expires</code> timestamp that is equal to <code>now()</code>, but how do I add <code>n</code> hours/days to it automatically?</p>