S3 service implementation for Rustack.

This crate implements the S3 business logic provider (RustackS3) that can be plugged into the rustack-s3-http service layer via the S3Handler trait. It supports bucket CRUD, object CRUD, multipart uploads, versioning, CORS, tagging, ACLs, encryption metadata, checksums, object lock, and more.

Architecture

rustack-s3-http (routing, XML, auth)
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       v
RustackS3 (S3Handler trait impl in server)
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       v
  S3ServiceState (buckets, global index)
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       v
  StorageBackend (in-memory + spillover)