Setup

1. copy .env.sample to .env

2. put your github app id and app secret to .env

3. bundle

4. rails s

Github OAuth flow

1. generate one authorize_url and ask the user to click on it

2. github will send a redirect request to user browser.

3. callback url that runs in your user browser, which actually calls your rails controller

4. use that code params to exchange long living access token for consecutive api call