Use slog logger and enable s3 http request logs

[johha]

PR #22 introduced slog for logging for S3, GCS and Ali. To ensure a consistent logging format this PR adopts slog for S3.
Additionally a new http logging middleware is added for S3 which prints request logs when needed (e.g. with flag -log-level debug). The existing middlewares.go has been renamed to accept_encoding_fix.go and moved to the s3middleware folder for clearer structure.

S3 Debug Log Format

S3 Debug Log Format

Non-Existing Blob

❯ ./storage-cli -c tmp/minio_aws.json -log-level debug -s s3 exists dummy.txt
{"time":"2026-01-30T13:23:08.638516+01:00","level":"DEBUG","msg":"s3 http request","method":"HEAD","url":"http://localhost:9000/storage-cli/dummy.txt","host":"","request_content_length":0,"duration_ms":2,"status_code":404,"response_content_length":0,"request_id":"188F81B3FDDA1418","extended_request_id":"dd9025bab4ad464b049177c95eb6ebf374d3b3fd1af9251148b658df7ac2e3e8"}
{"time":"2026-01-30T13:23:08.638982+01:00","level":"INFO","msg":"Blob does not exist in bucket","bucket":"storage-cli","blob":"dummy.txt"}
{"time":"2026-01-30T13:23:08.638988+01:00","level":"ERROR","msg":"performing operation","command":"exists","error":"object does not exist"}

Put Blob

❯ ./storage-cli -c tmp/minio_aws.json -log-level debug -s s3 put tmp/dummy.txt dummy.txt
{"time":"2026-01-30T13:23:13.479642+01:00","level":"DEBUG","msg":"s3 http request","method":"PUT","url":"http://localhost:9000/storage-cli/dummy.txt?x-id=PutObject","host":"","request_content_length":6,"duration_ms":5,"status_code":200,"response_content_length":0,"request_id":"188F81B51E3F2260","extended_request_id":"dd9025bab4ad464b049177c95eb6ebf374d3b3fd1af9251148b658df7ac2e3e8"}
{"time":"2026-01-30T13:23:13.480116+01:00","level":"INFO","msg":"Successfully uploaded file","location":"http://localhost:9000/storage-cli/dummy.txt"}

Existing Blob

❯ ./storage-cli -c tmp/minio_aws.json -log-level debug -s s3 exists dummy.txt
{"time":"2026-01-30T13:23:17.724548+01:00","level":"DEBUG","msg":"s3 http request","method":"HEAD","url":"http://localhost:9000/storage-cli/dummy.txt","host":"","request_content_length":0,"duration_ms":11,"status_code":200,"response_content_length":6,"request_id":"188F81B61AE43E38","extended_request_id":"dd9025bab4ad464b049177c95eb6ebf374d3b3fd1af9251148b658df7ac2e3e8"}
{"time":"2026-01-30T13:23:17.725054+01:00","level":"INFO","msg":"Blob exists in bucket","bucket":"storage-cli","blob":"dummy.txt"}

Get Blob

❯ ./storage-cli -c tmp/minio_aws.json -log-level debug -s s3 get dummy.txt dummy.txt
{"time":"2026-01-30T13:23:37.724995+01:00","level":"DEBUG","msg":"s3 http request","method":"GET","url":"http://localhost:9000/storage-cli/dummy.txt?x-id=GetObject","host":"","request_content_length":0,"duration_ms":2,"status_code":206,"response_content_length":6,"request_id":"188F81BAC3858188","extended_request_id":"dd9025bab4ad464b049177c95eb6ebf374d3b3fd1af9251148b658df7ac2e3e8"}

Delete Blob

./storage-cli -c tmp/minio_aws.json -log-level debug -s s3 delete dummy.txt
{"time":"2026-01-30T13:50:05.375201+01:00","level":"DEBUG","msg":"s3 http request","method":"DELETE","url":"http://localhost:9000/storage-cli/dummy.txt?x-id=DeleteObject","host":"","request_content_length":0,"duration_ms":8,"response_content_length":0,"request_id":"188F832C6A9FE630","extended_request_id":"dd9025bab4ad464b049177c95eb6ebf374d3b3fd1af9251148b658df7ac2e3e8","status_code":204}

[johha]

When the log level is not set to debug and an error occurs we still get meaningful error messages from AWS:

{"time":"2026-01-30T14:27:53.504115+01:00","level":"ERROR","msg":"performing operation","command":"exists","error":"failed to check exist: operation error S3: HeadObject, https response error StatusCode: 403, RequestID: 188F853C81E454B8, HostID: dd9025bab4ad464b049177c95eb6ebf374d3b3fd1af9251148b658df7ac2e3e8, api error Forbidden: Forbidden"}

[stephanme]

Non-existing blob:

./storage-cli -c tmp/minio_aws.json -log-level debug -s s3 exists dummy.txt
{"time":"2026-01-30T13:23:08.638516+01:00","level":"DEBUG","msg":"s3 http request","method":"HEAD","url":"http://localhost:9000/storage-cli/dummy.txt","host":"","request_content_length":0,"duration_ms":2,"status_code":404,"response_content_length":0,"request_id":"188F81B3FDDA1418","extended_request_id":"dd9025bab4ad464b049177c95eb6ebf374d3b3fd1af9251148b658df7ac2e3e8"}
{"time":"2026-01-30T13:23:08.638982+01:00","level":"INFO","msg":"Blob does not exist in bucket","bucket":"storage-cli","blob":"dummy.txt"}
{"time":"2026-01-30T13:23:08.638988+01:00","level":"ERROR","msg":"performing operation","command":"exists","error":"object does not exist"}

The last log-line should be on INFO and not on ERROR level. The "exists" operation returned the desired result and there was no problem with executing the request. Only the client can decide if a non-existing blob is an error or not.

For CAPI, ERROR logs for non-existing blobs would lead to log pollution for resource matching.

[serdarozerr]

looks good, just a minor suggestion added