Missing 639-3 language codes?

[qqmyers]

The updated citation metadata block has ISO 639-3 codes for many but not all languages listed in the block as an alternate value. Looking at table on https://en.wikipedia.org/wiki/List_of_ISO_639-1_codes which has a 639-3 column, I think all of the languages actually have a code. (639-3 sometimes has multiple codes for a 'macrolanguage' and it looks the citation block lists the macrolanguage, but these cases could have multiple alternates e.g. Bihari is in the block - bih is the 639-2 code and 639-3 maps it to three languages with codes bho, mag, and mai). Unless there's a reason some were left out, it might be useful to add them all at some point.

[jggautier]

Agreed. I can only speculate that only a subset of the ISO 639-3 codes were added because the only UI form component being used to select terms from a vocabulary didn't work well for vocabularies with 7000+ terms. Now that we have the drop down/type ahead UI component, it's easier to search for terms in lists that large.

I think this is related to #4589 and #7377