A trait which is implemented by the structures which are planned to translate the
configuration structures into pre-prepared instances. For example, there is a
CfgServer which is deserialized from the /etc/myprogram/server.shm which contains generic
fields like bind address encoded as String and may contain errors. A structure
ConfigServer which parses this data to IpAddr instance. It implements this trait in order to
be attached to CfgServer and called to fill its fields from CfgServer.