Support v4 signature for s3

[Ismael]

Currently Cloudflare R2 requires SigV4 for auth. I haven't found a way to set that up. Can this be added?

[gaul]

JCLOUDS-1594 added support for this by overriding jclouds.s3.signer-version=4. Can you test this and add an example to https://github.com/gaul/s3proxy/wiki/Storage-backend-examples?

[Ismael]

It works for downloads, it fails for PUT.

The error message from CF is that it doesn't support STREAMING-AWS4-HMAC-SHA256-PAYLOAD . Seems it should use UNSIGNED-PAYLOAD, do you know if this can be enabled in jclouds?

[gaul]

Unfortunately no and jclouds is a dead dependency. Please document what works today in the wiki and report a bug against Cloudflare.

[Ismael]

Added doc here:
https://github.com/gaul/s3proxy/wiki/Storage-backend-compatibility#cloudflare-using-s3-adapter

Thanks.

[musabshak]

I additionally added a comment here: https://github.com/gaul/s3proxy/wiki/Storage-backend-examples#s3-compatible-dreamobjects-etc

The idea of non-version controlled docs (Wiki) feels a bit iffy to me / I am new to GH wiki. Any chance someone could sanity-check the section I added for accuracy? @Ismael @gaul