[sap-document-ai]: Configurable result delivery channels

[samyuktaprabhu]

The plugin currently publishes extraction results only through the DocumentExtractionResult CDS event. Applications that require a different integration mechanism must adapt to this event model.

Introduce a pluggable result delivery mechanism that allows applications to configure how extraction results are delivered..

[github-actions]

👋 Hello @samyuktaprabhu, thank you for submitting this issue. Our team is reviewing your report and will follow up with you as soon as possible.

[lisajulia]

Closing since document-ai part will move to own repo in https://github.com/cap-java.