re-order notification dao delete notifications test to move "fixtures"
to the top of the file
changed create_service_data_retention to take an ORM object, not an id.
brings it in line with other db.py test functions
Admin app needs to get the service data retention for the specified
notification type, so to avoid iterating through the list of all
existing service data retention settings we restore the endpoint
to get the individual data retention period.
If the request is for the big numbers on the activity page, then we need to use the number right number of days.
Added an end point to get the data retention for the service and notification type, which is needed on the activity page to say how long the report is available for.
