Public discord webhook (#492)

migrations/20221206221021_webhook-sent.sql

@@ -0,0 +1,9 @@
+-- Add migration script here
+ALTER TABLE mods ADD COLUMN webhook_sent BOOL NOT NULL DEFAULT FALSE;
+
+UPDATE mods
+SET webhook_sent = (status = 'approved');
+
+UPDATE mods
+SET status = 'withheld'
+WHERE status = 'unlisted';