UX ONLY: User auth revisit

[uxarya-d]

Summary

Rethink user authorization from ground up to avoid existing+future bottlenecks related to auth. The goal is to make auth scalable and modular.

Motivation

User auth tends to become problematic when we need to enforce auth for new features.

Proposal

https://docs.google.com/document/d/1szpZP25OSye_MIoiZrJIjYW4eKZ7rcAvB0SLeVvLrnU/edit?usp=sharing