feat: wip, better digest handling (+ eventual digest resend logic) (#7995)

* feat: wip, better digest handling (+ eventual digest resend logic)

- await emailer.send call in digest.send method
- save send success to a new sorted set digest:{interval}:byUid

* feat: continuing work on digest tools

- Added ACP page to view digest settings and delivery times per user

* feat: added paginator and stub buttons for resending digest

* feat: wrapping up digest revamp

- New language strings in ACP digest page
- Client-side ACP script for digest ACP page
- Websocket call for ACP page to execute digests
- Broke out logic to retrieve user digest settings to getUsersInterval

* fix: minor cleanup

* fix: #8010 and some style suggestions from baris

* fix: resolve confusing comment

src/controllers/admin.js

@@ -9,6 +9,7 @@ var adminController = {
 	postQueue: require('./admin/postqueue'),
 	blacklist: require('./admin/blacklist'),
 	groups: require('./admin/groups'),
+	digest: require('./admin/digest'),
 	appearance: require('./admin/appearance'),
 	extend: {
 		widgets: require('./admin/widgets'),