[sap-document-ai]: Support push-based result delivery via Document AI outbound channels #106

Currently

The plugin currently polls Document AI to determine the status of extraction jobs. While functional, polling introduces additional latency and unnecessary requests.

Document AI also supports outbound channels at the schema level, including notification channels for status updates and extension channels for callbacks after prediction.

Idea

Investigate integrating the plugin with Document AI outbound channels so that extraction results and status updates are delivered via callbacks instead of polling.

This approach could eliminate the need for polling, reduce network overhead, and improve result delivery latency.