use branded types for messageType determination

server/helper/messageIdentifiers.ts

@@ -1,11 +1,20 @@
 import { Message } from "discord.js";
 
-export function messageIsVoteMessage(msg: Message): boolean {
+
+// branded types to differentiate objects of identical Type but different contents
+export type VoteEndMessage = Message & { readonly __brand: 'vote' }
+export type AnnouncementMessage = Message & { readonly __brand: 'announcement' }
+export type VoteMessage = Message & { readonly __brand: 'voteend' }
+
+export type DiscordMessage = VoteMessage | VoteEndMessage | AnnouncementMessage
+
+export function isVoteMessage(msg: Message): msg is VoteMessage {
 	return msg.cleanContent.includes('[Abstimmung]')
 }
-export function messageIsInitialAnnouncement(msg: Message): boolean {
+export function isInitialAnnouncement(msg: Message): msg is AnnouncementMessage {
 	return msg.cleanContent.includes("[initial]")
 }
-export function messageIsVoteEndedMessage(msg: Message): boolean {
+export function isVoteEndedMessage(msg: Message): msg is VoteEndMessage {
 	return msg.cleanContent.includes("[Abstimmung beendet]")
 }
+