Feature-Flag Rollout vs. Immediate OAuth2 Cutover for a Zero-Downtime Passport Migration
We run a small Express application that authenticates users with Passport's local strategy backed by server-side sessions (connect-mongo). The plan is to move to an OAuth2 authorization-code flow without forcing any user to log out mid-migration, and I need to commit to one of two documented approaches before writing code. Approach A is incremental: keep the