Data update Script: Backfill Created, but Unregistered Users (#10939) [deploy]

* Adds a data_update script to backfill registered for created, unregistered users

* Checks that invitation_accepted_at is nil and modifies return placement

* Removes user.created_at.nil check from data_update script

* Removes gaurd clause and fetches users from DB

lib/data_update_scripts/20201019192035_backfill_registered_for_users.rb

@@ -0,0 +1,10 @@
+module DataUpdateScripts
+  class BackfillRegisteredForUsers
+    def run
+      users = User.where.not(invitation_accepted_at: nil).where(registered: false).or(User.where(registered_at: nil))
+      users.find_each do |user|
+        user.update_columns(registered: true, registered_at: user.invitation_accepted_at)
+      end
+    end
+  end
+end