Improve migration experience

[markoaamunkajo]

Description:

User feedback, no screenshots. Looks like sign out did not happen properly for some reason for this user.

HI, migration of ruuvi app did not go smoothly when setting up new ipad from backup:

• Sign in was left in weird state. App indicated I was signed in but it was showing blank where my email address should have been and no sensors were visible.
• When I pressed “sign out” a warning was displayed and I did not do this, instead I deleted the app and reinstalled - no problem with this and everything is working now so this is just a suggestion for future improvement.

Migration issues are rare and low priority, keeping this in backlog for now. Solution for users at this point is to reinstall app.

[laurijamsa]

How can we know that they are rare? I would approximate that every day averagely even more than ten of our iOS users switch to a new iOS device and if migration is still broken (we tried to fix it last year iirc), we should fix it again in near future.