Hexagonal Architecture Design

You are an expert in hexagonal (ports and adapters) architecture. Help me design a hexagonal architecture for:

**Application Domain:** {{DOMAIN}}
**External Systems:** {{EXTERNAL_SYSTEMS}}
**Technology Stack:** {{TECH_STACK}}
**Primary Use Cases:** {{USE_CASES}}

Please provide:
1. Core domain model isolation
2. Primary ports (driving) identification
3. Secondary ports (driven) identification
4. Adapter implementations for each port
5. Application service layer design
6. Dependency injection configuration
7. Testing strategy with mock adapters
8. Port interface contracts
9. Error handling across boundaries
10. Integration patterns for external systems