S3Proxy 3.2.0

• Accept x-amz-checksum-{crc32,crc32c,sha1,sha256} headers, #765
• Add /healthz endpoint for health monitoring in S3Proxy, #763
• Bridge S3-only clients to SFTP storage, #1042
• Change provider defaults from deprecated jclouds to their SDK replacements
• Handle STREAMING-AWS4-HMAC-SHA256-PAYLOAD-TRAILER content-sha256
• Make /metrics return real Prometheus exposition
• Verify per-chunk signatures for STREAMING-AWS4-HMAC-SHA256-PAYLOAD, #205

Note that this is the last release to rely on Apache jclouds. Future releases will lack its Atmos, B2, or Swift providers.

Thanks @Aazme, @captainpacket, and @tejasae-afk for opening pull requests to improve S3Proxy!