Improve the onboarding routing

[ghengeveld]

From AP-4105

This is a general ticket to reference for a pr that aims to harden the routing and then potentially refactor it. Keeping it separate to allow us to focus on testing the happy path before trying to understand edge cases like browser refreshes, story changes, odd build edge cases, and more.

In QA we may choose to add subtasks here for found bugs in the routing, or choose to separate them out. Ideally they should be separately explicitly defined so that the work here is manageable.