[RFE] Brightbox official support

[tormath1]

Current situation

Brightbox images are built and release by the Flatcar CI but there is no documentation and no test for it.

Impact

We are not even sure that the images are working correctly

Ideal future situation

Brightbox support is documented and tested in the CI

Implementation options

There is a Go SDK for the Mantle implementation: https://github.com/brightbox/gobrightbox

• Use OpenStack image for Brightbox scripts#1391
• api/v1: support image creation brightbox/gobrightbox#39
• v2/images: remove source and add URL parameter brightbox/gobrightbox#40
• kola: add brightbox support mantle#484
• systemd/system/sshkeys: Make execution more robust init#112
• v2/servers: add docstring for userdata brightbox/gobrightbox#41
• ci-automation: add brightbox testing scripts#1419
• https://github.com/flatcar/jenkins-os/pull/322
• brightbox: initial commit flatcar-website#291

[tormath1]

Tested a Flatcar OpenStack image on Brightbox, it works fine - including Ignition and Afterburn. Sent a PR (brightbox/gobrightbox#39, brightbox/gobrightbox#40) to allow image creation from the Go SDK in order to investigate on a Mantle implementation for bringing test automation.