title: Where to store user id in jwt
body: <p>I am generting a jwt for an api token.  I am putting the user id into that jwt so I know who is calling into the api.  Where do I put the user id in the jwt.</p>
  
  <p>I have seen many different examples that put it in 'sub', 'aud' and even 'iss'.  Which is correct if any.  Or does user id go in a non registered name?</p>