Summary:
Depends on D2049
This change replaces the onboarding flow to include new graphics, copy, and
support for the new Nylas auth flow. New account choosing UI presents a list
of account types, rather than guessing based on an entered email. Pages before
and after introduce the user to different features of the client.
Known issue: Polling for gmail account connection works, but continues even if
you leave the page.
Test Plan: Manual testing.
Reviewers: evan
Reviewed By: evan
Differential Revision: https://phab.nylas.com/D2050
