Generate seed file presigned URL in crawl operator, update prior to expiry

[tw4l]

Fixes #3576

Changes

• Pass seed file id, not presigned url, to crawl job template, and generate presigned URL for seed files in crawl operator as needed
• Track presigned URL expiry and regenerate as needed before the URL expires

[mistydemeo]

Making sense to me. Since this has changed a model, I assume we need a corresponding migration?

[tw4l]

Making sense to me. Since this has changed a model, I assume we need a corresponding migration?

Normally we would but this model isn't serialized to the database, just used to corral data from the k8s crawl job into a format that's easier for us to work with.