hotfix: sentry issue 2266
https://push-notifications-sentry.web.cern.ch/sentry/jobs/issues/2266/?referrer=alert_email
Changes:
- Standardise PG image: init from dbdump
- scheduled notifications: fix routing payload
- remove unused fields
- add missing category field
- add default obj_dict to json.dumps
Edited by Carina Antunes