Store both user_id and email.
Store both user_id and email.

JonGal/appengine-ml-demo,ashwini0529/appengine-guestbook-python,Romzz/appengine-guestbook-python,thejeshgn/appengine-guestbook-python,JonGal/appengine-ml-demo,wcyuan/weather-mailer,t9nf/appengine-guestbook-python,jerarl/gcp-appengine-python,artificechicago/camp2016,GoogleCloudPlatform/appengine-guestbook-python,bkeyvani/appengine-guestbook-python,jeffgodwyll/appengine-flask-guestbook,adjohnson916/appengine-guestbook-python,dmolson/appengine-guestbook-python,jerarl/gcp-appengine-python,dmolson/appengine-guestbook-python,JackConnor/portfolio,bkeyvani/appengine-guestbook-python,t9nf/appengine-guestbook-python,Romzz/appengine-guestbook-python,ashwini0529/appengine-guestbook-python,jeffgodwyll/appengine-flask-guestbook,wcyuan/weather-mailer,GoogleCloudPlatform/appengine-guestbook-python,adjohnson916/appengine-guestbook-python,thejeshgn/appengine-guestbook-python,JackConnor/portfolio,artificechicago/camp2016