Feature/api v2

[quarian]

Contains the doc updates for the migration to a v2 version of the API. Compatibility on the data model level is preserved, but consumers should inspect the new API and its behaviour.

Since THL has started publishing their data, all the health care districts don't do it anymore (this makes sense). This makes updating our old style of observation based API too much work. I thought of weaving the updating THL data into our old style data, but decided agains it.

Main reason is this: we reported data based on the reporting date of the observations, and THL reports based on the testing date. We could always place the new observations on the current date if we kept our eyes open and it would offer a whole picture. That doesn't mesh well with the testing based updates (how to make sure we don't report things twice)? How would this mesh with our historical data?

By using just one of the sources we can offer a meaningful picture of the events. So consider our first API the history of the reporting of the coronavirus cases, and the new THL API the factual testing history.

This should interest @Matsuuu @VuokkoH @valstu @duukkis @Julleht @kallehjerppe @Miksus @jonniek @ultsi @mouhgang @pauliinasol @Karvaporsas @jhamberg @lovelldies @AnttiHaerkoenen @Avicted @Marantle @jussivirkkala @eevajonnapanula @jingzhe @lounjukk @Tatatofly .

[EsaMakinen]

This is a good approach. There is a minimal change required for all data-using apps, but I hope and think it's doable. This will ensure that nothing is broken downstream and we will continue supplying data.