Publish a DRUID as part of the public MODS record

[cbeer]

It would be a nice courtesy for harvesters and other consuming our metadata if our public MODS documented included the DRUID (and a URL to the PURL record? a URL to a IIIF manifest? etc).

Maybe the DRUID would be appropriate in the mods:identifier or mods:recordInfo/mods:recordIdentifier? We also have some existing records (mostly geo?) that encode this as<recordIdentifier>edu.stanford.purl:bg149mk9437</recordIdentifier>.

This may also be part of a larger task to publish a more complete recordInfo record for our public mods?