Use the UN M.49 code for regions and continents

The UN has an official code for regions (continents) and subregions. https://en.wikipedia.org/wiki/UN_M.49
We would like to use that in the counttry module as continents. Currently the code used in this module is a selfmade code (1S etc).
One issue is that we can't add them as the database only allows 2 characters for continents and the regions are 3 digits.