message: Prevent duplicates whitelist users
diff: @@ -41,6 +41,8 @@ const whitelistUserSchema = new mongoose.Schema({
  }
  }
  });
  +// Prevent duplicates in one course.
  +whitelistUserSchema.index({ uid: 1, courseId: 1}, { unique: true });
  const WhitelistUser = mongoose.model<IWhitelistUserModel>('WhitelistUser', whitelistUserSchema);
  