add stream item clearing to job if production

This was causing problems when there were too many stream item instances
that needed to be dealt with inside the transaction.

fixes LA-923
fixes LA-922
flag=none

Change-Id: Idccffb6206aaa3c8a28dd7b1be713018a5ee388e
Reviewed-on: https://gerrit.instructure.com/c/canvas-lms/+/234220
Tested-by: Service Cloud Jenkins <svc.cloudjenkins@instructure.com>
Reviewed-by: James Williams <jamesw@instructure.com>
Reviewed-by: Rob Orton <rob@instructure.com>
QA-Review: Rob Orton <rob@instructure.com>
Product-Review: Rob Orton <rob@instructure.com>

app/models/discussion_topic.rb

@@ -929,6 +929,10 @@ class DiscussionTopic < ActiveRecord::Base
     # either changed sections or made section specificness
     return unless self.is_section_specific? ? @sections_changed : self.is_section_specific_before_last_save
 
+    send_later_if_production(:clear_stream_items_for_sections)
+  end
+
+  def clear_stream_items_for_sections
     remaining_participants = participants
     user_ids = []
     stream_item&.stream_item_instances&.find_each do |item|
@@ -942,12 +946,16 @@ class DiscussionTopic < ActiveRecord::Base
   end
 
   def clear_non_applicable_stream_items_for_delayed_posts
-    user_ids = []
     if self.is_announcement && self.delayed_post_at? && @delayed_post_at_changed && self.delayed_post_at > Time.now
-      stream_item&.stream_item_instances&.find_each do |item|
-        user_ids.push(item.user_id)
-        item.destroy
-      end
+      send_later_if_production(:clear_stream_items_for_delayed_posts)
+    end
+  end
+
+  def clear_stream_items_for_delayed_posts
+    user_ids = []
+    stream_item&.stream_item_instances&.find_each do |item|
+      user_ids.push(item.user_id)
+      item.destroy
     end
     self.clear_stream_item_cache_for(user_ids)
   end