Acceptance criteria:

• The old Kessel dependencies are removed from Notifications.
• The new Kessel SDK is added to Notifications.
• All permissions are checked at the workspace level using the default workspace provided by RBAC.
• The default workspace is retrieved from RBAC through the Kessel SDK.
• No changes are made yet to the Notifications schema in Kessel.
• No data migration should be needed.
• QE tests validate the permission checks with Kessel API v2.