Release v0.4.0

[donatello]

Summary

• Bump package version from 0.3.0 to 0.4.0 in Cargo.toml ahead of the 0.4.0 tag and crates.io publish.

No code changes beyond the version bump. Release notes below for review — I'll use these as the GitHub release body once the tag is cut.

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Proposed release notes (v0.4.0)

Breaking changes

• Typed wrapper structs for string parameters — most API methods now accept TryInto<BucketName> / TryInto<ObjectKey> / etc., so &str / String / pre-validated typed values all work at call sites. Validation happens once at the boundary. (Refactor string parameters to typed wrapper structs #200)
• Error type cleanup and reorganization. (Refactor/cleanup errors #179)
• Request builders migrated to the TypedBuilder derive macro — builder surface is regenerated; some method shapes may differ. (use crate TypedBuilder for builders #184)
• Credential provider type simplified from Arc<Box<dyn CredentialProvider>> to Arc<dyn CredentialProvider>. (fix: replace Arc<Box<...>> credential-provider with Arc<...> #164)
• DeleteObjects batching lowered from 10,000 to 1,000 keys per request to match the documented S3 limit. (fix: batch DeleteObjects at 1000 keys, not 10_000 #208)
• Default multipart part size raised to 64 MiB (from the previous default, via an intermediate 16 MiB step). (feat: use 16 MiB default part size for multipart uploads #207, feat: use 64 MiB default part size for multipart uploads #209)

New features

• Request hooks infrastructure — intercept and modify in-flight requests, e.g. for load balancing. (feat: add request hooks infrastructure #188, see examples/load_balancing_with_hooks.rs)
• Additional checksum algorithms: CRC32, CRC32C, SHA1, SHA256, and CRC64NVME. (added checksum support CRC32, CRC32C, SHA1, SHA256 and CRC64NVME #195)

Performance

• Signing key memoization; stat_object now issues HEAD instead of GET. (performance optimizations: Signing key caching, stat_object to use HEAD #197)
• Eliminated intermediate Vec<Bytes> allocation during HTTP request body preparation. ( Removed unnecessary intermediate Vec<Bytes> allocation in HTTP request body #192)

Fixes

• Virtual-hosted-style bucket requests now use / as the URL path. (fix: set URL path to "/" for virtual-hosted-style S3 bucket requests #205)
• Two bugs fixed in AppendObjectContent multipart append. (fix: correct two bugs in AppendObjectContent multipart append #206)
• Correct part size in multipart copy; added missing response properties. (Fix incorrect part size in multipart copy #196)
• rustls can now be used alongside sha2 and hmac. (fix: allow to use rustls while also using sha2 and hmac #175)
• Form-decoding (not percent-decoding) is used for whitespace in URLs during signing. (Bugfix: whitespace in object name #178)
• delete_and_purge_bucket deletes objects recursively. (bugfix: delete_and_purge_bucket add recursive delete #166)
• HTTP header constants use proper capitalization. (fix: update HTTP header constants to use proper capitalization #186)

Housekeeping / internal

• Codebase consolidation and test infrastructure refresh. (refactor: consolidate codebase structure and add testing infrastructure #194)
• Test macro for parameterized integration tests. (feat: add a test macro #170)
• Duplicated code removed; lazy response evaluation. (Duplicated code removed, and lazy response evaluation #162)
• Dropped direct tokio / tokio-stream / tokio-util dependencies; library internals now use runtime-agnostic futures-util / async-stream combinators. Tokio is still pulled in transitively via reqwest / hyper, so a tokio-compatible runtime is still required at the call site. (moved Tokio runtime from general dependency to dev dependency #167)
• Clippy cleanup and unused-import pruning. (fixed clippy issues and cleanup of unnecessary imports #182, Tests cleanup; cargo clippy fixes, minor doc updates #177)
• copy_object documentation. (Add documentation about source/destination of copy_object #172)
• Added .github/copilot-instructions.md. (Add .github/copilot-instructions.md for repository onboarding #191)

Full commit range: v0.3.0..release-v0.4.0 (26 commits).

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Test plan

• cargo fmt --all --check clean
• cargo clippy --all-targets — zero warnings
• cargo test --doc passes
• cargo test --lib --bins passes
• cargo build --all-targets succeeds
• cargo publish --dry-run (to run before tagging)
• Tag v0.4.0 after merge and publish to crates.io
• Run ./deploy-docs.sh to refresh rustdoc on gh-pages

[HJLebbink]

LGTM