Manage redirect metadata on feed file objects in S3

[farski]

Once the CDN supports it, we should be able to set the redirect metatdata (x-amz-meta-dovetail-feed-cdn-redirect) through the UI.

I guess there's a choice to make about whether this is podcast-level, or feed-level. I don't think we ever offboard just a feed, but the value is set on each discrete feed file in S3.

[farski]

Maybe MVP some way to lock the feed file so it can't be republished and overwrite the S3 file that has the metadata set on it

[cavis]

Maybe the podcast.locked boolean? Would need to double check how that gets used in the code, but this is sort of its intent.

Or a completely new boolean, to indicate "this podcast was redirected". Even if we're still setting S3 metadata manually.