Allow including Content-MD5 in S3 object uploads

[rpadaki]

Is your feature request related to a problem? Please describe.

This is required to use SFTP-Go with Object Lock enabled buckets. You just need to compute the hash and include in each put object or upload part call: https://docs.aws.amazon.com/AmazonS3/latest/userguide/object-lock-managing.html#object-lock-put-object

Describe the solution you'd like

In s3fs.go, in the singlePartUpload and uploadPart methods, we should add md5 calculation logic. To prevent any regressions, I think this should be opt-in via a boolean option, which requires some frontend changes. Additionally, we'd need to update the config type in https://github.com/sftpgo/sdk.

Describe alternatives you've considered

No response

What are you using SFTPGo for?

Medium business

Additional context

I actually sketched out most of the required code changes locally and would be happy to open a PR if I can get confirmation that the above approach looks right.

[drakkan]

I believe we should implement a more generic integrity check support (instead of adding the Content-MD5 header) which would also address compatibility issues with buckets that have Object Lock enabled. This is why we moved away from the S3 Manager (used in version 2.6) and transitioned to the low-level S3 API, which gives us greater control and makes it easier to add features like this.

This feature is planned for inclusion in the December release of our Enterprise Edition and may be added to the open-source version at a later stage.

Thank you for offering to submit a PR. Based on our past experience, reviewing and iterating on external contributions can sometimes take more time than implementing the change ourselves, so we’ll handle this one internally. It’s a fairly simple change now that we’ve rewritten the code to remove the dependency on the S3 Manager. We really appreciate your willingness to contribute, though.