Pass complete event to denormalization function

[elmarx]

Currently, when registring a callback to the denormalization-service, the callback has two parameters: oldData and payload.

If the message-structure is configured to NOT contain the aggregate-id in the payload, there's currently no way to access the aggregate-id inside the denormalization function.

[adrai]

Advice: message structure should NOT be hard-coded (evt.payload)