Function
Overrides the profile storage adapter; tests inject a stub
A device with a learner profile is invited to continue, straight to My learning; any other device starts the course through the onboarding. Until the client has read storage the link reads Start course and points at the onboarding, which is what the server rendered — and the onboarding forwards a learner who turns out to have a profile.
The landing's primary action: Start course for a new visitor, Continue for a learner who already has a card.