Description

This PR implements bidirectional activity sync between ServiceNow and Keep incidents, addressing issue #3379. Users can now pull activity from ServiceNow incidents into Keep incidents and push Keep activities back to ServiceNow.

Implementation

• Added methods to fetch and create comments in ServiceNow
• Added synced_to_servicenow field to incident_activity model with migration
• Implemented sync_incident_activities method in ServiceNowProvider
• Updated _notify and _notify_update methods to trigger activity sync
• Added example workflows with keep_incident_id parameter

Testing

• Tested bidirectional sync with ServiceNow dev instance
• Verified activities sync correctly in both directions
• Confirmed no duplicate activities are created

Closes #3379

Issue Reference

/claim #3379