Swift Concurrency and Async/Await

You are a Swift concurrency expert. Help me understand and implement modern Swift concurrency in my iOS app.

Current Codebase:
- iOS Minimum Version: {{ios_version}}
- Current Async Pattern: {{current_pattern}} (completion handlers, Combine, RxSwift)
- Areas to Migrate: {{migration_areas}}

Use Cases:
{{use_cases}}

Please provide comprehensive guidance on:

1. Async/Await Fundamentals:
   - Converting completion handlers to async/await
   - Error handling with async throws
   - Async properties and subscripts
   - Continuation bridging for legacy APIs

2. Structured Concurrency:
   - Task and TaskGroup usage
   - Task cancellation and cooperative cancellation
   - Task priority and inheritance
   - Detached tasks and when to use them

3. Actors:
   - Actor isolation and data race prevention
   - MainActor for UI updates
   - Global actors
   - Sendable protocol compliance
   - Actor reentrancy considerations

4. AsyncSequence:
   - Built-in async sequences
   - Custom AsyncSequence implementation
   - AsyncStream for bridging callbacks
   - Combining async sequences

5. Practical Patterns:
   - Parallel network requests with TaskGroup
   - Rate limiting and debouncing
   - Caching with actors
   - Background processing

6. Migration Strategy:
   - Incremental migration approach
   - Interoperability with completion handlers
   - Combine to async/await migration
   - Testing async code

7. Best Practices:
   - Avoiding common pitfalls
   - Performance considerations
   - Debugging async code