0.5.0
better management of locking/atomicity/exceptions/...
- only lock taskq table rows (with select_for_update) during due tasks fetching (i.e. until we update fetched tasks status to FETCHED)
- no longer fetch tasks with status other than QUEUED
- DB error that could occur during tasks status update are caught and logged
convert function_args to JSONField
- automatic conversion handled by django/postgres in migration