[RFE] Support alternative tempurl algorithms for swift

[Jim Rollenhagen]

Swift now supports multiple algorithms for tempurls: "The tempurl digest algorithm is now configurable, and Swift added support for both SHA-256 and SHA-512. Supported tempurl digests are exposed to clients in /info. Additionally, tempurl signatures can now be base64 encoded."

from https://github.com/openstack/swift/blob/b33941feda95b8e37c5bb68a2a5cdfe2007e3a4d/releasenotes/notes/2_17_0_release-bd35f18c41c5ef18.yaml#L28-L32

We'll need to support these, as different algorithms can be enabled. We'll need to check /info for supported algorithms and generate the tempurl based on that. That said, I'm not sure we require swift creds just to use the tempurl stuff, so we might have to start requiring those for features that use tempurls.

[Ruby Loo (rloo)]

TheJulia sez: I'm good without a spec as long as there are not any additional mechanics to reach out to swift. If it works like the existing client for generation then \o/. Reaching out might require more, and even with some lightweight client driven mechanics, I don't think it really needs a spec, it is just an additional capability in my mind.

[Ruby Loo (rloo)]

I'm good with this, with similar caveats to TheJulia in comment #1. There is no API change, and I don't think we need a config change. (Hmm, if a config change is needed, then we need to discuss...)

I'm going to approve it. We can always unapprove if it gets more complicated than we envision.