PIN verification, notifications, multiple notif providers

Discord, Email & Telegram can be enabled, although email is always
enabled right now (will fix). Also apparently markdown hyperlinks don't
work in Discord, eventually will implement something to convert them to
embeds.

html/form-base.html

@@ -17,6 +17,9 @@
     window.telegramEnabled = {{ .telegramEnabled }};
     window.telegramRequired = {{ .telegramRequired }};
     window.telegramPIN = "{{ .telegramPIN }}";
+    window.discordEnabled = {{ .discordEnabled }};
+    window.discordRequired = {{ .discordRequired }};
+    window.discordPIN = "{{ .discordPIN }}";
 </script>
 <script src="js/form.js" type="module"></script>
 {{ end }}