리텐션
리텐션을 측정하는 세 가지 방법
https://blog.ab180.co/posts/retention-series-3-1
GA
Rubular: a Ruby regular expression editor
https://rubular.com/Super URL Builder for Google Analytics - Google Sheets
https://docs.google.com/spreadsheets/d/1ho8ty_B08aIWvo3rLGvkulG-QrmLGzAEGQ1my3Aspsg/edit#gid=440544775