Oracle Cloud Object Storage: Additional Authentication Methods and Enhancements

## Overview

Follow-up issue for Oracle Cloud Object Storage AFS adapter to implement additional authentication methods and enhancements that were deferred from the initial implementation in #35 (merged in #36).

## Background

The initial Oracle Cloud Object Storage adapter implementation (#36) successfully delivered:
- ✅ Config file authentication
- ✅ Instance principal authentication
- ✅ Core connector functionality
- ✅ Path validation
- ✅ Unit tests
- ✅ Documentation

However, some features were marked as future work and need to be implemented.

## Remaining Tasks

### 1. Resource Principal Authentication
**Priority**: Medium
**Effort**: ~4 hours

- [ ] Implement `ResourcePrincipalAuthenticationDetailsProvider` support
- [ ] Add configuration methods for resource principal
- [ ] Update `OracleCloudObjectStorageConfiguration.CreateResourcePrincipalProvider()`
- [ ] Add unit tests for resource principal configuration
- [ ] Update documentation with resource principal examples

**Use Case**: Required for OCI Functions to authenticate without storing credentials.

**Implementation Notes**:
```csharp
private IBasicAuthenticationDetailsProvider CreateResourcePrincipalProvider()
{
// Research correct OCI .NET SDK API for resource principal
// Current placeholder throws NotImplementedException
return ResourcePrincipalAuthenticationDetailsProvider.Build();
}
```

### 2. Simple Authentication with Direct Credentials
**Priority**: Low
**Effort**: ~6 hours

- [ ] Implement simple authentication using user OCID, tenancy OCID, fingerprint, and private key
- [ ] Add configuration methods: `SetSimpleAuth(userOcid, tenancyOcid, fingerprint, privateKeyPath, passphrase)`
- [ ] Handle private key file reading and parsing
- [ ] Add region configuration for simple auth
- [ ] Add unit tests for simple authentication
- [ ] Update documentation with simple auth examples

**Use Case**: Useful for testing and scenarios where config file is not available.

**Implementation Notes**:
```csharp
private IBasicAuthenticationDetailsProvider CreateSimpleProvider()
{
// Research correct constructor signature for SimpleAuthenticationDetailsProvider
// May need to read private key file and convert to appropriate format
return new SimpleAuthenticationDetailsProvider(
tenancyOcid: TenancyOcid,
userOcid: UserOcid,
fingerprint: Fingerprint,
privateKeyPath: PrivateKeyPath,
passphrase: PrivateKeyPassphrase?.ToCharArray()
);
}
```

### 3. Custom Endpoint Configuration
**Priority**: Low
**Effort**: ~2 hours

- [ ] Research how to set custom endpoint in OCI .NET SDK
- [ ] Implement endpoint configuration in `OracleCloudObjectStorageConnector.New()`
- [ ] Add validation for custom endpoint URLs
- [ ] Add unit tests for custom endpoint
- [ ] Update documentation

**Use Case**: Required for using OCI-compatible storage services or testing with local emulators.

**Current Code**:
```csharp
// Note: Custom endpoint configuration would need to be set via ClientConfiguration
// if needed in the future
```

### 4. Integration Tests
**Priority**: High
**Effort**: ~8 hours

- [ ] Create integration test project
- [ ] Set up test OCI bucket and credentials (use environment variables)
- [ ] Implement tests for:
- [ ] File upload/download
- [ ] Large file multipart upload (>5 GiB)
- [ ] Directory operations
- [ ] File move/copy operations
- [ ] Concurrent operations
- [ ] Error handling (network failures, permission errors)
- [ ] Add CI/CD integration (optional, may require OCI credentials in CI)
- [ ] Document how to run integration tests

**Note**: Integration tests require actual OCI account and credentials.

### 5. Performance Benchmarks
**Priority**: Medium
**Effort**: ~6 hours

- [ ] Create benchmark project using BenchmarkDotNet
- [ ] Benchmark scenarios:
- [ ] Small file operations (< 1 MB)
- [ ] Medium file operations (1-100 MB)
- [ ] Large file operations (> 100 MB)
- [ ] Concurrent operations
- [ ] Caching vs non-caching performance
- [ ] Compare with other AFS adapters (AWS S3, Azure Storage)
- [ ] Document performance characteristics
- [ ] Identify optimization opportunities

### 6. Additional Enhancements
**Priority**: Low
**Effort**: Variable

- [ ] Add support for OCI Object Storage lifecycle policies
- [ ] Add support for object metadata
- [ ] Add support for server-side encryption configuration
- [ ] Add support for object versioning
- [ ] Implement progress callbacks for large uploads
- [ ] Add support for pre-signed URLs
- [ ] Optimize blob listing for large directories (pagination improvements)

## Success Criteria

- [ ] All authentication methods working and tested
- [ ] Integration tests passing with real OCI Object Storage
- [ ] Performance benchmarks documented
- [ ] Documentation updated with all examples
- [ ] No breaking changes to existing API

## Dependencies

- OCI .NET SDK documentation: https://docs.oracle.com/en-us/iaas/Content/API/SDKDocs/dotnetconcepts.htm
- OCI .NET SDK GitHub: https://github.com/oracle/oci-dotnet-sdk
- Existing implementation: `afs/oraclecloud/objectstorage/`

## Related Issues

- #35 - Original migration request (closed)
- #36 - Initial implementation PR (merged)

## Notes

- Tasks can be implemented incrementally in separate PRs
- Integration tests and benchmarks may require OCI account setup
- Resource principal and simple auth require research into correct OCI .NET SDK APIs
- Consider creating separate issues for larger tasks (integration tests, benchmarks)