Global testing dataset from OWID

[MatMoore]

This is another potential data source we could use: https://github.com/owid/covid-19-data/blob/master/public/data/testing/covid-testing-all-observations.csv

Context: https://ourworldindata.org/covid-testing

Like the John Hopkins Dataset:

• it's updated daily
• it contains records from different countries, which we could map to country codes.

Unlike JH:

• they provide sources for each record
• they don't correct past data (the numbers reflect what is known at commit time)