Simplify MBID validation for direct editing
Simplify MBID validation for direct editing

It's way too slow to validate that the MBIDs are actually valid, but
we can at least validate that they are well-formed UUIDs and not worry
about whether or not they are valid until they are used.

wuvt/wuvt-site,wuvt/wuvt-site,wuvt/wuvt-site,wuvt/wuvt-site