Migrate to new storage endpoints use. All package loaders will benefit from it directly.
Impacts identified (diff on their way):
tox
I don't find the name and docstring explicit enough, but I don't have any better idea for the name :/
why not switch to passing model objects instead of converting them back to dicts?
contents_for_storage, prepare_contents_for_storage?
because right now, it's not supported. so might as well convert here to avoid impacts in other callers.
Build is green See https://jenkins.softwareheritage.org/job/DLDBASE/job/tox/323/ for more details.