Add support for Server-Side Encryption with AWS Key Management Service
(SSE-KMS) for S3 object storage. This allows Nextcloud to encrypt data
at rest in S3 using AWS-managed keys.
Key features:
- New config options: sse_kms_enabled and sse_kms_key_id
- Backward compatible with existing SSE-C (customer-provided keys)
- SSE-C takes precedence when both SSE-C and SSE-KMS are configured
Implementation details:
- Added getServerSideEncryptionParameters() method to centralize
encryption parameter logic for both SSE-C and SSE-KMS
- Updated multipart uploads to use unified encryption parameters
- Added comprehensive PHPUnit tests for SSE-KMS scenarios
- Tested with AWS bucket and KMS keys in us-east-1 region
Co-Authored-By: Claude Sonnet 4.5 (1M context) <noreply@anthropic.com>
Signed-off-by: Stephen Cuppett <steve@cuppett.com>
