Open requested to merge generated-differential-D8759-source into master
This revision adds payload and payload type fields to the ExtID class. The intent is to use these fields to store Disarchive specifications to support recovering source tarballs.
See https://sympa.inria.fr/sympa/arc/swh-devel/2022-02/msg00022.html where Stefano suggests using a generic payload mechanism for ExtIDs and https://sympa.inria.fr/sympa/arc/swh-devel/2022-05/msg00027.html where we decided on using object storage for the payload.
Migrated from D8759 (view on Phabricator)