Since it is meant to be the base to use class to wrap any db access.
This imply:
[x] extract the code from swh.storage in swh.core (D996)
[] rewrite scheduler's swh.scheduler.backend.SchedulerBackend class (T1494)
[x] refactor swh.storage.db.BaseDb (D997)
[] swh.vault.backend (D1108)
[x] swh.indexer.storage.db