최재은 / 밀당강의봇

1. app.js
- API Endpoint ( Receive requests from Facebook page and start to make request to Facebook Graph API )
- Open port ( app.listen(PORT_NUMBER) ), Perform verification ( app.get('/webhook') )
- Use/Call Handler function from controller.js

2. controller.js
- Handle Message or Postback
- Use/Call model.js / template.js to make response
- Make request to Facebook's Graph API ( Messaging Platform ) using response, sender_psid

3. template.js
- Make JSON format using data given from controller.js
- Return JSON format ( to be  'response' object in controller.js )

4. models.js
- Get data from database.
- Give data required by controller.js.