Feature: Thumbnails sourced from Solr -- not Manifests

[markpbaggett]

Is your feature request related to a problem? Please describe.
Currently, we have complex issues related to our presentation manifest generation tool. If a manifest is not cached, manifest generation can take over an hour. We also know that manifest generation for works with many parts can actually block requests for cached manifests.

In order to limit unnecessary requests to irIIIFService and accidentally cause a disruption in manifest fetching, thumbnail requests should target the Solr core and thumbnails should be available by default.

Describe the solution you'd like
The Solr core has a thumbnail of the file related to the iana:first property for every work in a collection and that item is Solrized in a thumbnail field in Sage. The thumbnail can be generated from Cantaloupe using a Base64 encoding request.

Describe alternatives you've considered
This would be even better if we modeled thumbnail on a work in Fedora and had MagPie or whatever tooling we use to deposit data create resources. That would allow someone to choose thumbnails on deposit or even after.

Additional context
Add any other context or screenshots about the feature request here.