Implement audit trail for private data access events

[Soushi888]

Overview

Implement an audit trail system that logs all private data access events (grants, access, revocations) for compliance and governance purposes.

Background

The capability-based sharing system (#27) handles grant/access/revocation but does not log these events for auditing. The original design included an audit_and_notifications.rs module that was never implemented.

Implementation

Create audit logging for:

• Grant creation events (who granted what fields to whom, with expiration)
• Data access events (who accessed what data, when)
• Grant revocation events (who revoked, reason if provided)
• Grant expiration events (automatic expiration detection)

Consider using Holochain entries or signals for audit events.

Files to Create/Modify

• dnas/nondominium/zomes/coordinator/zome_person/src/audit_and_notifications.rs (new)
• dnas/nondominium/zomes/coordinator/zome_person/src/lib.rs (register module)
• dnas/nondominium/zomes/integrity/zome_person/src/lib.rs (audit entry types if needed)

Acceptance Criteria

• Audit entry type defined for private data access events
• Grant creation logged automatically
• Data access logged automatically
• Grant revocation logged automatically
• Query function to retrieve audit trail for a specific agent
• Test coverage for audit trail creation and retrieval

Related

• Completed in Implement Enhanced Private Data Sharing System #27: Core capability-based sharing system