lang_code_transform

Define alpha-3 to alpha-2 language code transformations.

Defines dict LANG_CODE_TRANSFORM for tranformation of offial European Union languages from ISO 639-2 (alpha-3 codes) to ISO 639-1 (alpha-2 codes).

The transformations are needed for year 2020 ESEF reports when requirements to report the language in the file name were obscure. They affect the resolution of derived attribute Filing.language.