Return a "to" field for statuses
When posting a status we have the ability to send a "to" field (explicit addressing).
There's some work to create a UI supporting this, but it has to parse mentions from the content of the parent post to prefill it: https://gitlab.com/soapbox-pub/soapbox-fe/-/merge_requests/930
It would be better if the parent post just returned the whole "to" field (ideally, in the same format as mentions, and without non-actor URIs).
We already have in_reply_to_acct
, but it's not quite enough as it only returns the author of the parent post.