HIPAA-Compliant Patient Data Anonymization Schema

Design a robust database schema that automatically anonymizes patient records while preserving referential integrity and research utility. Create a solution that can handle PHI masking, encryption, and selective data exposure with granular access controls. Include mechanisms for audit logging, versioning, and reversible anonymization that meets HIPAA's strict de-identification requirements. Provide sample migrations and ORM mappings that demonstrate how sensitive fields like SSN, birthdate, and contact information can be securely transformed.