Get access to self reference OR to the reference of an Event sender

[sledorze]

The use case is to send an Event to a parent state Machine (actually 2 parent levels up) and that parent receiver would know the ActorRef of the sender

child relation: SMA => SMB => SMC

SMC sends an event holding its Ref to SMA
Note: either because

• it is part of the Event (which is not the case - we have actionMeta._event.origin but it's not the ActorRef)
• we're able to access the self ref in SMC (always or even at creation time) and fill the ref into the Event

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as a work around; I'll send a message to the SM just after creation to feed it its Ref ; but that's a bit stretchy :)