Interface of the partial function used by the ShardRegion to extract the entity id and the message to send to the entity from an incoming message. The implementation is application specific. If the partial function does not match the message will be `unhandled`, i.e. posted as `Unhandled` messages on the event stream. Note that the extracted message does not have to be the same as the incoming message to support wrapping in message envelope that is unwrapped before sending to the entity actor.

public delegate Tuple<string, Object> IdExtractor(
	Object message
)

type IdExtractor = 
    delegate of 
        message : Object -> Tuple<string, Object>