Add one day to the new users range (#16065)

The download app broadcast (in the Generator) returns early if the
user was created less than 7 days ago. It seems counterproductive to
filter out _only_ users created in the last 7 days.

Add one day to the query range, so users created less than 8 days ago,
but more than 7 days ago, receive the final message.

app/workers/broadcasts/send_welcome_notifications_worker.rb

@@ -5,18 +5,18 @@ module Broadcasts
     sidekiq_options queue: :medium_priority, retry: 15
 
     def perform
-      # In order to prevent new users from receiving multiple welcome notifications in a day,
-      # a feature_live_date is required. The script will only be effective after feature_live_date
-      # and will ultimately be superseded by 7.days.ago when it's larger than feature_live_date.
       return unless Settings::General.welcome_notifications_live_at
 
       User.select(:id).where("created_at > ?", created_after).find_each do |user|
+        # the Generator ensures only one notification is created per user per day
         Broadcasts::WelcomeNotification::Generator.call(user.id)
       end
     end
 
     def created_after
-      [Settings::General.welcome_notifications_live_at, 7.days.ago].max
+      # The script will only be effective after feature_live_date
+      # and will ultimately be superseded by 8.days.ago when it's larger than feature_live_date.
+      [Settings::General.welcome_notifications_live_at, 8.days.ago].max
     end
     private :created_after
   end