tldr; Channels are just FIDs with USER_DATA_IS_CHANNEL=true
For this proposal, a channel is a currated set or chronologically ordered casts. A channel is identified by an FID,
let's call it channelfid
and the corresponding fname, @channelfname
.
When a user wants to post to a channel, they just mention @channelfname
.
In order for their cast to be "added" to the channel: