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)