Upload service feedback stats to pp: basic flow
Extend ServiceFeedback to calc aggregate stats
Service feedback aggregated metrics
Add missing ServiceFeedback#transaction_slugs
Add logging to service feedback uploader
Whenever integration for scheduled pp uploads
Put redis lock around service feedback upload

This ought to prevent multiple nodes from pushing multiple times.

This code is ahem.. borrowed volatile lock code from alphagov/signonotron2
Fix bug in whenever schedule, add missing bracket
Bump to released gds-api-adapters version and update tests