Embed Notice

@devnull My code does something like this:

```
const publicRecipients = await getPublicRecipients(activity) // to, cc, audience
const privateRecipients = await getPrivateRecipients(activity) // bto, bcc

const publicInboxes = await getSharedOrDirectInboxes(publicRecipients)
const privateInboxes = await getDirectInboxesOnly(privateRecipients)

await Promise.all(deliverToAll(publicInboxes, activity), deliverToAll(privateInboxes, activity))
```