[cinder] cinder backup benji driver.

Hi, I have been looking into using benji-backup[1] in a cinder-backup driver[2].

I have not tested it thoroughly enough yet, but both in devstack and in a multinode setup.(focal victoria).

On devstack I get a newer sqlalchemy that satisfies Benji's requirements list. I have not found issues with downgrading Benji to use an earlier version of sqlalchemy found in canonical focal repos. But that also needs some testing. I asked the author of Benji why he chose a version as high as he did.

So just a little info about this work. Any comments on the idea?

Thanks. Jesper Schmitz Mouridsen.

[1] https://benji-backup.me/ [2] https://github.com/jsm222/cinder-backup-benji-driver