Codes here are mostly ISO 639-1 (two-letter, e.g.
en, fr) with some
ISO 639-3 / regional and Ollang-specific variants for locales that need them
(for example pt-PT, es-MX, ar-EG, zh-Hant, fr-CA, en-UK). A few
codes are platform-specific historical assignments — pass the exact string
shown in the table when constructing sourceLanguage or language values.
If you see a code returned by the API that isn’t in this table, treat the
API response as authoritative and let us know via support.