Add support for kafka journalization of the ProvenanceStorageInterface
the new ProvenanceStorageJournal is a proxy ProvenanceStorageInterface that will push added objects in a swh-journal (typ. a kafka).
Journal messages are simple dicts with 2 keys: id (the sharding key) and value (a serialiazable version of the argument of the xxx_add() method).
Depends on !152 (closed) Related to #4616 (closed)
Migrated from D8657 (view on Phabricator)