add validator for languageTerm of type code with no authority, or no authority matching iso-639*

[ndushay]

motived by https://app.honeybadger.io/projects/50568/faults/103801039

I did PR sul-dlss/mods/pull/59 to silence this in the MODS gem, which is the wrong approach.

JLitt suggested in slack: "write a validator, then run validation with a cocina gem branch and see what fails. Avoids the need for a report."

The work for this ticket is

• [ ] to write a validator to check that when a languageTerm of type code is provided, there is always an authority starting with "iso-639" as the mods code desires. Do this in a branch on cocina-models gem
• [ ] run validation using branch to get a list of the druids failing validation and send it to Arcadia for remediation
• [ ] once data is remediated, run the validation again
• [ ] turn validation on

[arcadiafalcone]

We also use the code list rfc5646, and there are probably still some with marclanguage floating around in our data. Those are the ones I know are in use, but everything on this list is valid: https://www.loc.gov/standards/sourcelist/language.html. So the validation should either check for all of those codes or not check the code value.

[peetucket]

Example druid with issue from HB:

{"identifier" => "druid:dv940wx4544"}

[ndushay]

I believe the problem was actually that dor-services-app had stanford-mods pinned to version 2.6; version 3.3.9 does NOT give this error for sw_language_facet.

sul-dlss/dor-services-app/pull/4689 addresses this and has been deployed to prod

I'm closing this. If we need such a thing, Arcadia will ask for it. :-P