Make snapshot_add validate its input.
Depends on !822 (closed), !241 (closed), and swh-model!46 (closed).
Migrated from D1878 (view on Phabricator)
Staging instance, all changes can be removed at any time
Depends on !822 (closed), !241 (closed), and swh-model!46 (closed).
Migrated from D1878 (view on Phabricator)