Evergreen should allow different control sets/thesauri based on 6XX indicator 2 and $2

[Jane Sandberg]

We'd like our 650s with 2nd indicator=0 to just validate against our LCSH and local authorities, and 650s with 2nd indicator=2 to just validate against MeSH headings. Currently, I can add a "650_0$aAutistic Disorder" to a bib record and it will validate just fine, even though "Autistic Disorder" is a MeSH term, not an LoC one.

Better behavior would be to have a separate control set for MeSH headings that only is consulted when the 2nd indicator=2, indicating the contents are a MeSH term.

The same goes for the $2 when the 2nd indicator=7. For example, for the bib field

$650 _7$aFantasmas$vNovela juvenil.$2qlsp

There's no need to consult any of our thesauri except the qlsp one.