adding feature flags

[kkchu791]

Fixes #2042

What changes did you make and why did you make them ?

Implementing posthog feature flags from backend to frontend. It's event driven architecture where a request is made to PostHog when client user refreshes.

1. Event Driven Approach (Chose this one because less complicated and we have small enough Daily Active Users where the client requests won't be an issue. If it does become an issue, we can try the second approach with SSE.)

2. Server Sent Events Approach ( Decided not to do this approach because the open connection adds complexity to the app which I don't think is needed. The benefits of this approach don't outweight the complexity it brings.)

Screenshots of Proposed Changes Of The Website

[trillium]

• Want to know how to change flags for specific users
• Roll back functionality as awhole for all users in app
• Roll out features to a subset of users

[kkchu791]

• Want to know how to change flags for specific users

• We can search for the users distinct Id in PostHog and turn on/off his flag.

• Roll back functionality as awhole for all users in app.

We can do immediate roll backs by switching the feature flag to on/off.

• Roll out features to a subset of users.

We can roll out by a certagin percentage. We can also create cohorts to roll out to if we want to turn on a feature for specific users.

@trillium let me know if you want me to add any of these functionality to the POC.