Provide possibility to push partition key for Kafka based eventbus

[Hronom]

Is your feature request related to a problem? Please describe.
Currently there no possibility to set partition for message pushed to event bus based on kafka.

Describe the solution you'd like
Provide possibility to push some metadata in event sources that can be used by underlying event bus implementation.

Describe alternatives you've considered
Have reserved fields in message body that can be extracted event bus during send of message to the underlying messaging system.

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