ChainStep<Input, Output> constructor

Base class for all chain processing steps that defines type-safe data transformation and error handling behavior.

Key features:

• Type-safe input/output handling
• Asynchronous processing support
• Error handling with rollback
• Extensible through mixins

Example:

class ValidationStep extends ChainStep<RequestData, RequestData> {
  @override
  Future<RequestData> handle(RequestData data, ChainContext context) async {
    if (!isValid(data)) throw ValidationError();
    return data;
  }

  @override
  Future<void> rollback(RequestData data, ChainContext context) async {
    // Cleanup logic
  }
}