feat(boost-greeting): implement randomized greeting messages

Introduce a collection of greeting templates to provide variety when
a user boosts the server. The system now selects a random message
from the available variants and logs the selected variant index.

src/discord/events/boostGreeting.test.ts

@@ -13,7 +13,6 @@ describe("sendBoostGreeting", () => {
     await sendBoostGreeting(channel, "user-123", "channel-456");
 
     expect(sent.length).toBe(1);
-    expect(sent[0]).toContain("Makasih udah ngeboost");
     expect(sent[0]).toContain("<@user-123>");
     expect(sent[0]).toContain("/booster-role claim");
     expect(sent[0]).toContain("di sini");

src/discord/events/boostGreeting.ts

@@ -1,7 +1,20 @@
 import { logger } from "../../logger";
 
+const greetings = [
+  (userId: string) =>
+    `🎉 Makasih udah ngeboost <@${userId}>! Sekarang kamu bisa claim custom role pake \`/booster-role claim\` di sini.`,
+  (userId: string) =>
+    `🔥 <@${userId}> baru aja ngeboost! Langsung aja claim custom role kamu pake \`/booster-role claim\` di sini.`,
+  (userId: string) =>
+    `✨ Thank you <@${userId}> for the boost! Claim custom role kamu pake \`/booster-role claim\` di sini ya.`,
+  (userId: string) =>
+    `👑 <@${userId}> ngeboost server! Yuk langsung claim custom role pake \`/booster-role claim\` di sini.`,
+  (userId: string) =>
+    `🎊 Ada booster baru nih, <@${userId}>! Jangan lupa claim custom role kamu pake \`/booster-role claim\` di sini.`,
+];
+
 /**
- * Sends a welcome message via the given channel when a member newly
+ * Sends a random welcome message via the given channel when a member newly
  * acquires the booster eligibility role (i.e. just boosted the server).
  */
 export async function sendBoostGreeting(
@@ -9,11 +22,10 @@ export async function sendBoostGreeting(
   userId: string,
   greetingChannelId: string,
 ): Promise<void> {
-  const message =
-    `🎉 Makasih udah ngeboost <@${userId}>! ` +
-    `Sekarang kamu bisa claim custom role pake \`/booster-role claim\` di sini.`;
+  const pick = Math.floor(Math.random() * greetings.length);
+  const message = greetings[pick](userId);
 
   await channel.send({ content: message });
 
-  logger.info("Boost greeting sent", { userId, channelId: greetingChannelId });
+  logger.info("Boost greeting sent", { userId, channelId: greetingChannelId, variant: pick });
 }