This user's global unique identifier.
For devices running iOS version 12.4 and later, IUserProfile.id returns GKPlayer.teamPlayerID.
For devices running iOS version 12.3 and earlier, IUserProfile.id returns GKPlayer.playerID.
Use IUserProfile.id instead of UserProfile.legacyId. Only use UserProfile.legacyId if you need to access GKPlayer.playerID to migrate player data in your existing project.