fix(storage): Review MinIO issues and evaluate S3 integration

[Yoo-SH]

Description

Review current MinIO implementation for any issues and evaluate the option to integrate AWS S3 or S3-compatible storage.

Current Issues to Check

• MinIO connection stability
• File upload/download reliability
• Docker volume persistence
• Bucket initialization on startup
• Error handling and retry logic

Investigation Tasks

• Review MinIO logs for errors or warnings
• Test file upload edge cases (large files, concurrent uploads)
• Check bucket lifecycle and cleanup policies
• Verify file integrity after storage
• Test recovery after service restart

S3 Integration Evaluation

• Compare MinIO vs AWS S3 vs other S3-compatible services
• Cost analysis for different storage options
• Migration path from MinIO to S3
• Configuration flexibility (support both MinIO and S3)
• Performance comparison

Proposed Solution

Create abstraction layer for object storage to support multiple backends:

public interface ObjectStorageService {
    void uploadFile(String path, InputStream content);
    InputStream downloadFile(String path);
    void deleteFile(String path);
}

// Implementations:
// - MinIOStorageService
// - S3StorageService

Configuration Options

opencontext:
  storage:
    type: minio  # or 's3'
    minio:
      endpoint: http://minio:9000
      access-key: minioadmin
      secret-key: minioadmin123!
    s3:
      region: ap-northeast-2
      bucket: opencontext-files

Files to Review

• core/src/main/java/com/opencontext/config/MinioConfig.java
• File upload/download service implementations
• docker-compose.yml MinIO configuration

Decision Criteria

• Reliability and stability
• Cost effectiveness
• Ease of deployment
• Backup and recovery capabilities
• Support for self-hosted deployment