Consider changing attachments endpoint variant behavior #40
Description
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As a separate issue, these changes makes me think we are maybe making things difficult for ourselves by making variant optional in the attachments endpoint. I also wonder whether the observations endpoint should return all variant URLs, e.g.
originalUrl,previewUrl,thumbnailUrl. When writing related frontend code it seems like this would be helpful for the non-cloud server work too.
Relates to digidem/comapeo-core#409.
We may want to return all variant URLs from the observations endpoint.