In order to track whether a particular user has seen an onboarding feature e.g. the "What's New"-Dialogue we need an API to store this information per user.
The idea is to have a generic api where we can store this state based on a particular key per user.
- a new secured endpoint GET /api/onboarding/:key is available that returns a boolean specific to the calling user
- a new secured endpoint PUT /api/onboarding/:key is available that allows to store a seen flag
- allowed keys are configured, invalid keys rejected with a 404
- the only key needed now would be whatsnew
- the endpoints are documented