feat: implement Polly resilience policies for database connections (#48)

[mikemcdougall]

Summary

Implements Polly resilience policies for database connection reliability as specified in Issue #48.

Closes #48

Key Changes

🔄 Resilience Implementation

• Connection retry policy with exponential backoff (3 retries, 100ms × 2^attempt)
• PostgreSQL error filtering - Only retries safe connection errors:
  • 57P03 (cannot_connect_now)
  • 08000 (connection_exception)
  • 08003 (connection_does_not_exist)
  • 08006 (connection_failure)
• Transaction safety - NO retries within transactions to prevent duplicate operations

📊 Observability

• Structured logging for retry attempts (Event ID 4040)
• Correlation ID support for request tracing
• Seamless integration with existing logging infrastructure

🏗️ Architecture

• NpgsqlDataSourceExtensions for clean integration
• Updated implementations:
  • PostgresFeatureStore - All CRUD operations use retry
  • PostgresLayerCatalog - All metadata queries use retry
• Vertical slice organization maintained

🧪 Testing

• 18 comprehensive tests covering all retry scenarios
• Error code validation for PostgreSQL states
• Integration tests with real database connections
• Edge case handling (timeouts, cancellation, callbacks)

Quality Assurance ✅

• All 104 tests passing (102 integration + 2 architecture)
• Zero build warnings/errors
• AOT compilation verified - 23MB binary (no regression)
• Runtime performance confirmed - Health checks <1ms
• Code formatting applied - dotnet format completed

Acceptance Criteria Met ✅

• ✅ Connection acquisition retries on transient errors
• ✅ Transactions are NOT retried (prevents duplicates)
• ✅ Retry attempts logged with correlation ID
• ✅ Policy integrates seamlessly with NpgsqlDataSource
• ✅ Follows documented MVP_PLAN.md patterns exactly

Technical Implementation

// Usage example - transparent to existing code
await using var connection = await _dataSource.OpenConnectionWithRetryAsync();

Files Changed: 10 files, +394 insertions
New Components: ResiliencePolicies, NpgsqlDataSourceExtensions, comprehensive test suite

🤖 Generated with Claude Code

[github-actions]

🤖 LLM Architecture Review

🚫 Assessment: BLOCKING_ISSUES

🏗️ Architecture Review Summary

✅ Good Patterns Found:

• Usage of dependency injection for PostgreSQL services in src/Honua.Postgres/ServiceCollectionExtensions.cs ensures modularity and ease of configuration changes.
• Implementation of resilience policies in src/Honua.Postgres/Features/Infrastructure/Resilience/ResiliencePolicies.cs and NpgsqlDataSourceExtensions.cs enhances the reliability of database connections.
• Comprehensive logging throughout the application, such as in src/Honua.Server/Features/Infrastructure/Logging/Log.cs, aids in monitoring and debugging.

⚠️ Architecture Concerns:

• Critical: Core depending on Infrastructure in src/Honua.Core/Features/Infrastructure/Abstractions/IDatabaseConnectionProvider.cs violates the dependency rule (Core should not depend on Infrastructure). This is a blocking issue.
• Warning: The PostgresLayerCatalog and PostgresFeatureStore classes in src/Honua.Postgres/Features/Catalog/PostgresLayerCatalog.cs and src/Honua.Postgres/Features/FeatureStore/PostgresFeatureStore.cs expose database-specific implementations which should be internal but are potentially accessible due to the project structure.
• Warning: Synchronous operations in async context observed in src/Honua.Postgres/Features/HealthCheck/PostgresDatabaseHealthChecker.cs with ConfigureAwait(false) used inconsistently.

💡 Recommendations:

• To resolve the critical dependency violation, refactor IDatabaseConnectionProvider to be part of a shared kernel or an abstraction layer that does not depend on any specific infrastructure.
• Ensure all database-specific implementations are marked as internal and are not exposed outside the Infrastructure layer. Use InternalsVisibleTo only when absolutely necessary.
• Standardize the use of ConfigureAwait(false) across all asynchronous operations to maintain consistency and prevent deadlocks in a mixed sync/async environment.

📚 Educational Notes:

• Dependency Direction: Keeping Core independent of Infrastructure is crucial in a Clean Architecture to ensure that business rules can evolve without being impacted by external concerns like database specifics.
• Resilience and Logging: Implementing resilience patterns such as retries with exponential backoff and comprehensive logging helps in maintaining the reliability and observability of the system, which is vital for high-availability applications such as geospatial feature servers.
• Async Best Practices: Consistent use of asynchronous programming best practices, including proper use of ConfigureAwait(false), is important to prevent performance bottlenecks and enhance the scalability of the application, especially under high load in a cloud-native environment.

Overall Assessment: BLOCKING_ISSUES

CRITICAL: The PR is linked to a GitHub issue with clear acceptance criteria, and changes address those criteria. However, the violation of Core depending on Infrastructure is a blocking issue that must be resolved before merging.

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This review focuses on architectural patterns and design decisions
Human review still recommended for complex changes