FIX: Prevent "uploads are missing in S3" alerts after restoring a backup

After restoring a backup it takes up to 48 hours for uploads stored on S3 to appear in the S3 inventory. This change prevents alerts about missing uploads by preventing the EnsureS3UploadsExistence job from running in the first 48 hours after a restore. During the restore it  deletes the count of missing uploads from the PluginStore, so that an alert isn't triggered by an old number.

app/models/backup_metadata.rb

@@ -6,6 +6,16 @@ class BackupMetadata < ActiveRecord::Base
   def self.value_for(name)
     where(name: name).pluck_first(:value).presence
   end
+
+  def self.last_restore_date
+    value = value_for(LAST_RESTORE_DATE)
+    value.present? ? Time.zone.parse(value) : nil
+  end
+
+  def self.update_last_restore_date(time = Time.zone.now)
+    BackupMetadata.where(name: LAST_RESTORE_DATE).delete_all
+    BackupMetadata.create!(name: LAST_RESTORE_DATE, value: time.iso8601)
+  end
 end
 
 # == Schema Information