Add preview images to subject sets

[eatyourgreens]

For Engaging Crowds, we'd like to show a preview image for each subject set (similar to the project cards that are used to list projects.) Ouroboros used to serialise the locations of 5 preview subjects with each subject set/group. Would it be possible to serialise the first 5 subject locations from a subject set, with the set? Or maybe set up a cards route similar to the cards route for projects?

[camallen]

Do you want this to be a curated set of image locations or just randomly selected?
We've got the metadata object on subject_sets

panoptes/app/serializers/subject_set_serializer.rb

Lines 6 to 7 in 679bd8d

	attributes :id, :display_name, :set_member_subjects_count, :metadata,
	:created_at, :updated_at, :href

that could be used to store this information.

Alternatively we could look to do something more formal with the resource links like you mention, a subject_sets.cards relation.

[eatyourgreens]

I was thinking the first few subjects, in order. If this is being used mainly to preview volumes for transcription workflows, then that would give us the title pages as a preview.

[eatyourgreens]

For the time being, I think I’m going to make a second request for the first subject of each set, unless there’s a faster way to get the linked subject?

[eatyourgreens]

Currently I'm using set_member_subjects to get the preview image for each set, which is turning out to be pretty fast anyway.
https://github.com/zooniverse/front-end-monorepo/blob/892120c64c016edc2f6b11aa88eabef44055e9e1/packages/app-project/src/screens/ProjectHomePage/components/Hero/helpers/fetchWorkflowsHelper/fetchWorkflowsHelper.js#L29-L38

[camallen]

closing this in favour of the approach outlined in #3451 (comment)