Non-MD5 Etag returned for objects

[roman-khimov]

Current Behavior

Known, documented, we return SHA256 hash in Etag.

Expected Behavior

Applications expect MD5 in some cases. See #1030 (comment)

Possible Solution

Probably this can be conditional. AWS docs mention that MD5 is used in a limited number of cases and these cases can be OK for us. We can also consider calculating/storing MD5, search is pretty much the same for payload hash and some S3-specific attribute. Yeah, MD5 sucks, but who cares when we can't provide compatibility with real applications.

Steps to Reproduce

Run Nexus3 against S3 gateway.

Context

https://docs.aws.amazon.com/AmazonS3/latest/userguide/checking-object-integrity.html

Regression

No.

Your Environment

• Version of the product used: 0.34.0

[roman-khimov]

https://docs.aws.amazon.com/AmazonS3/latest/API/RESTCommonResponseHeaders.html also