Github repo:
https://github.com/corsego/02-03-04-telegrails
Live demo:
https://telegrails.herokuapp.com
Useful resources:
https://core.telegram.org/widgets/login

0:00 Intro
0:27 Login widget
7:37 Save current user in Session
14:18 Log out (delete data from Session)
18:30 TelegramMailer to send private messages