Integrate growthBook for A/B testing.
We would like to have it works on both frontend ( different UI ) and backend ( switching processor )
AC:
- Integrate in payment wiki frontend for UI update
- Integrate in the backend to control the gateway switch
- Add experimental feature in frontend
- Add experimental feature in payment processor
- Add more log-related feature flags and store info in the log for experimental A/B testing comparison
- Add feature flag for those new feature with internal tester only rule
- document the usage of GrowthBook in WikiTech.