Merge Spinque/VGWW additions back to YUAG

[azaroth42]

Data catalog lists the datasets: https://data.spinque.com/ld/data/vangoghworldwide/datacatalog.jsonld

And then can harvest by incrementing offset:
https://rest.spinque.com/4/vangoghworldwide/api/platform/e/artworks/results?count=100&offset=100

The UI has more information than this representation, so must need to be pieced back together from multiple datasets.

[kkdavis14]

the dataset exports are all in nt :/ and all helpfully named "export.nt"

Are there other endpoints for things like the Letters and Bibliography?

The Letters can be gotten in XML pre-conversion but this isn't super useful. Probably best would be adding a link from our LUX page in referred_to_by to the Letters page, e.g.:
https://vangoghletters.org/vg/letters/let676/letter.html

so for example if we were trying to piece together YUAG's Night Cafe:

what's in the data at the artwork API isn't much more than what we have currently (though obvs this would be useful for objects we don't own).

to get Letters without endpoint:
connect two nts via bnode.
nt1: bnode note string > schema/mentions > VGWW uri
nt2.: van gogh letters uri but stripped to the "letNNN" bit (e.g. http://vangoghletters.org/orig/**let801**/annotation/n-27) > w3.org/body > bnode note string

example:
nt1: _:note_a16ef278-9db7-4ba3-a478-945159ee0db4-0-c1bd9a http://schema.org/mentions https://vangoghworldwide.org/data/artwork/F463
nt2: http://vangoghletters.org/orig/let801/annotation/n-27 http://www.w3.org/ns/oa#body _:note_a16ef278-9db7-4ba3-a478-945159ee0db4-0-c1bd9a

once we have "letNNN" == VGWW ID, we can add as a clickable link in LUX notes.
Letters html url looks like:
https://vangoghletters.org/vg/letters/let801/letter.html

to get Bibliography without endpoint:
??? does not seem to be one of the data sources in datacatalog.jsonld, unless it is RKD collections, but...see below:
searching RKD's online portal:
RDK collections appears to be archives, but all the objects in the forms-part-of triple in the collections.nt are library uris.
Am not sure what https://data.rkd.nl/document/ uris do. They don't resolve.
Poked around with the triples for a while without satisfactory results.