The release tag client/v7.0.0 is for VolumeSnapshot and VolumeGroupSnapshot APIs and client library which are in a separate go package.

Changes by Kind

API Change

• Add VolumeGroupSnapshot API definitions. (#814, @RaunakShah)
• The VolumeGroupSnapshotSource.Selector is now an optional attribute, so that a pre-provisioned VolumeGroupSnapshotContent can be specified which does not require a matching label-selector. (#995, @nixpanic)
• Update API for pre provisioned group snapshots (#971, @RaunakShah)

Full Changelog

https://github.com/kubernetes-csi/external-snapshotter/blob/v7.0.0/CHANGELOG/CHANGELOG-7.0.md