Expose thumbnails on works if the only restrictions are on the physical items

[alexwlchan]

Quoting Branwen in Slack:

I was wondering why a thumbnail image sometimes appears on Works and other times not? We recently ingested a set of 10 Royal Botanic Gardens prints, but only one has a thumbnail - https://wellcomecollection.org/works/xfq9r7ym (b32890783)
The others appear like this: https://wellcomecollection.org/works/u6snm6q6 (b32890345)

[alexwlchan]

Okay, so I went to have a look at this.

b32890345 is a combination of Sierra physical bib and a METS work, which has two items:

• a physical item, which has the access status "by appointment"
• a digitised item, which has the access status "open"

The merger suppresses thumbnails if any of the items on the work have restrictions, but in this case I think it's being overzealous – although the physical item has restrictions, we should be fine to display a digitised thumbnail.

I think we should suppress thumbnails only if the digitised item (i.e. the METS work) has restrictions.

I'm going to leave this ticket for now, with two notes:

1. @jtweed should confirm if that's the correct behaviour
2. if it is the correct behaviour, this would be a good first merger patch for somebody

[jtweed]

I think that's the correct behaviour, ie the thumbnail restrictions should come from the digitised work not the physical work.

[alexwlchan]

Paul fixed this!