... by directly storing it from the API which already provides a
three-digit, INSEE-compliant, 0-padded department code.

> %w[9740082W 7200011Z 0340045P].map { |uai| EstablishmentApi.fetch!(uai)["records"][0]["fields"]["code_departement"] }
> ["974", "02B", "034"]

- etab -> establishments ;
- don't go through WebMock (that's the EstablishmentApi spec's job) ;
- use a "dehydrated" establishment to avoid flaky specs.

The SYGNE API returns the result within a "scolarite" hash which
contains the latest schooling for that student by date of
creation (says their documentation).

Instead of assuming it's the latest open schooling, try and re-match
the schooling and only then update whatever can be updated, at the
moment only the status code which is "AP" for apprentices.

we cover pretty much the same thing in paiements.feature

Sometimes the APIs stop returning data for a certain INE. This usually
means that the student has changed INE (which happens more frequently
than we thought), and means we end up with duplicated data that we
cannot delete or ignore.

Store the result on the student table for now, and we can deal with
how to deal with them later.

This means including all the model validation like correct dates and
SEPA-ribs, etc.