feat(user)!: enhance user tag getter (#4652)

* feat: enhance user tag getter

* feat(user): add `0000` condition and better jsdoc for tag

* chore(user): use this keyword instead of destructuring assignment

* fix(user): correct isLegacy logic

packages/bot/src/transformers/types.ts

@@ -1784,7 +1784,7 @@ export interface User {
   banner?: bigint
   /** data for the user's avatar decoration */
   avatarDecorationData?: AvatarDecorationData
-  /** The user tag in the form of username#discriminator */
+  /** The user tag in the form of `username` or `username#discriminator` for legacy username system */
   tag: string
   /** Whether the user belongs to an OAuth2 application */
   bot: boolean

packages/bot/src/transformers/user.ts

@@ -11,7 +11,8 @@ export const baseUser: User = {
   ...(undefined as unknown as User),
 
   get tag() {
-    return `${this.username}#${this.discriminator}`
+    const isLegacy = this.discriminator !== '0' && this.discriminator !== '0000'
+    return isLegacy ? `${this.username}#${this.discriminator}` : this.username
   },
   get bot() {
     return !!this.toggles?.has('bot')