[Flow] Converting Objects by additional identity does not work?

[Carsten Bleicker]

hi folks,
having an entity with the default flow persistence identity and also another identity:

// @Flow\Entity
class Foo{
	
	/**
	* @var string
	* @Flow\Identity
	*/
	protected $foreignIdentity;
	
}


my routing:
-
	name: 'Read Action with foreignIdentity as {foo}'
	uriPattern: 'rest/{foo}'
	httpMethods: ['GET']
	defaults:
		'@package':    'Foo.Bar'
		'@controller': 'Foo'
		'@action':     'read'
		'@format':     'json'


I would expect that my controller receives the mapped entity, detected either by its foreignIdentity or by its flow_persistence_identifier.
But only flow_persistence_identifier works.

Am i wron with my expectation?