UI to view/edit channel subscribers

[chrisbobbe]

The legacy app doesn't quite offer a UI for this; it has an "Add subscribers" button, but that doesn't let you see who's currently subscribed, or let you remove subscribers (if you have permission for that):

Like #1102, this won't be ripe to work on until we're set up to handle the new group-based permissions. See at least can_remove_subscribers_group, for removing subscribers; there may be more permission groups to check.

Related issues

• Edit some channel settings #1102

[chrisbobbe]

This came up in beta feedback on CZO:

In the new app, I don't see any way to unsubscribe / mute / notifications / add subscriber.

From a bundle of channel-related actions, this is one that that user said he'd miss most or use most frequently:

Primarily unsubscribe, pin, and add/check subscribers.