map country codes used by european commission that don't follow the I…
…SO 3166-1 alpha-1 standard to their correct expressions
Please have a look at "Imperfect implementations" third paragraph: https://en.wikipedia.org/wiki/ISO_3166-1_alpha-2
Maybe you don't want duplicate regexes, let me know and I will clean it up.
Looking closer I see that this is taken care of in the decompose_vat_number function for Greece, however I still think it should have the same logic for GB/UK. I can add this if the maintainer is interested?
This is moot now, but for the record (I got quite confused for a while after reading this issue), the EU did use the official ISO 3166-1 alpha-2 code for the United Kingdom, GB. The UK uses the .uk TLD though, but that is a different can of worms.