To start with this will be an attribute on the service, at the time the notification is created it will look at Service.letter_class to decide what class to use for the letter.
This PR adds Service.letter class as a nullable column.
Updated the create_service and update_service method to default the value to second.
Subsequent PRs will add the check constraint to ensure we only get first or second in the letter_class column and make that column nullable.
This can't be done all at once because it will cause an error if someone inserts or updates a service during the deploy.
79815b4f8a