Use `thumbnail_url` for thumbnail generation when present

[stacimc]

Problem

Some providers (like SMK) may link to quite large images in their image_url. This can cause unacceptably slow response times or even timeouts when generating thumbnails via our thumbnail service.

Description

We already have a thumbnail_url available on the Image model which we can use.

When the thumbnail_url is available, we should send this to the thumbnail service instead of the image_url. This should be a small change here:

image_url = image.thumbnail or image.url

(using the serialized field names)

Additional context

https://github.com/WordPress/openverse-catalog/issues/698 tracks updating the SMK provider script in the Catalog to populate thumbnail_url with a link to a smaller image size.

Implementation

• [ ] 🙋 I would be interested in implementing this feature.

[sarayourfriend]

Just a heads-up, the field name in the API right now is just thumbnail not thumbnail_url: https://github.com/WordPress/openverse-api/blob/2e85caf7aede8aaf9d77cd5cb050f50b860ee58e/api/catalog/api/models/mixins.py#L92