Allow Internal and Carrier users access to all shipments on a manifest
Internal and Carrier users should have permission to see all shipments on a manifest, regardless of the shipment's importer.
External users who are not carriers should only see shipments for importers that they have access to. This includes inability to see shipments that have no importer filled in.
Prevent editing of multi-importer manifests for non-carrier external users
Internal and Carrier users should have permission to edit (delete, submit, ...) manifests regardless of the importer(s) whose shipments are on the manifest.
External users who are not carriers can only edit a manifest if they have access to all importers whose shipments are on the manifest. If any of the shipments has no importer, the user cannot edit.