Basic NeoFS ACL applies access rules to request sender. Request
senders are combined in groups that calls `targets`.
Basic ACL rules may be applied to these targets:
1. User - request sender is the owner of the container,
used in the request.
2. System - request sender is the storage node
within the container used in the request or
inner ring node.
3. Others - request sender is none of the above.
Extended ACL rules may be applied for targets, provided with
extra information.
4. PubKey - request sender has provided public key.
