receive
Accept this demand and start processing it: transitions it through RECEIVED → IN_PROCESS at receiver. Equivalent to the two-call sequence receive(receiver); process(receiver) but named for the intent ("the receiver has taken the demand and is now responsible for finishing it").
After this call returns, the demand sits at IN_PROCESS waiting for whatever the receiver needs to do (forward upstream, lead-time delay, backlog wait) before completion. Pair with fulfillAndDispatch to finish the demand once the work is done.
Required precondition: this demand is in the SENT state. Calling from any other state raises the same IllegalStateException that the underlying state machine would have raised.
Parameters
the filler taking custody of the demand (typically the routing node or cloner itself)