Added and used scheduleDeletion

...only where I was certain that whis was a good idea,
perhaps it could be useful in more places.

utils/tg.js

@@ -1,5 +1,11 @@
 'use strict';
 
+const { telegram } = require('../bot');
+
+const { promisify } = require('util');
+
+const delay = promisify(setTimeout);
+
 const escapeHtml = s => s
 	.replace(/</g, '&lt;');
 
@@ -21,9 +27,18 @@ const deleteAfter = ms => ctx =>
 		ctx.telegram.deleteMessage(ctx.chat.id, ctx.message.message_id),
 	ms);
 
+const scheduleDeletion = async ({ chat, message_id }) => {
+	if (chat.type === 'private') {
+		return null;
+	}
+	await delay(5 * 60 * 1000);
+	return telegram.deleteMessage(chat.id, message_id);
+};
+
 module.exports = {
 	deleteAfter,
 	escapeHtml,
 	link,
 	quietLink,
+	scheduleDeletion,
 };