- Add IamConfig field to S3ApiServerOption for optional advanced IAM
- Integrate IAM loading logic directly into NewS3ApiServerWithStore
- Remove duplicate enhanced_s3_server.go file
- Simplify command line logic to use single server constructor
- Maintain backward compatibility - standard IAM works without config
- Advanced IAM activated automatically when -iam.config is provided
This follows better architectural principles by enhancing existing
functions rather than creating parallel implementations.