This setting limits the number of users in a direct message. 0 means you can only create a direct message with yourself.
Co-authored-by: David McClure <dave@xerotrope.org>
This is a followup of the previous refactor where we created two new
models to handle all the dedicated logic that was present in the
`ChatChannel` model.
For the sake of consistency, `DMChannel` has been renamed to
`DirectMessageChannel` and the previous `DirectMessageChannel` model is
now named `DirectMessage`. This should help reasoning about direct
messages.