Add updated openssh to support git signing

[jo-basevi]

Using the Gadi's system git and ssh (version OpenSSH_8.0p1), attempting to sign commits with git commit -S with an ssh signing key gives:

error: ssh-keygen -Y sign is needed for ssh signing (available in openssh version 8.2p1+)

So to support git signing, we have been using an ssh-keygen executable in an payu conda environment that has an openssh installed with an updated version (see section in dev-docs). It would be great to have this executable accessible outside of a payu conda environment.

[aidanheerdegen]

OpenSSH spack package:

https://packages.spack.io/package.html?name=openssh

Is there a preference for a version to install? The most recent version in our 0.22 spack fork is 9.7p1:

https://github.com/ACCESS-NRI/spack/blob/releases/v0.22/var/spack/repos/builtin/packages/openssh/package.py#L28

Feel free to assign yourself and make a PR @atteggiani or @jo-basevi

[jo-basevi]

The payu/1.1.5 module uses 9.8p1, so probably prefer 9.7p1 as it's most up to date (?) but the main thing is >8.2p1 I think

[aidanheerdegen]

If we think it's more straightforward we can add 9.8p1 to our spack fork.

[atteggiani]

From the OpenSSH release notes, 9.8p1 version seems to be fixing a critical security problem about 9.7p1. Not sure how much this would matter, but I would try to add the 9.8p1 to our spack packages and use that.

[atteggiani]

I'm happy to do both, so I can get more familiar with Spack packages since I've never got the time to really understand that deeply.

[jo-basevi]

Thanks @atteggiani, I am not familiar with spack packages either so I would be curious to have a look at the PRs - even though I won't be qualified to properly review them!