cloud-init support for KVM

[arpadszasz]

User story

The so called cloud images (like the ones provided by Canonical for Ubuntu) expect a YAML metadata to be provided for provisioning basic features like creating users / adding SSH keys / etc and is achived using cloud-init.

The provisioning is useful to be able to use an out-of-the-box image vs. having to bake one yourself with specific user/password and SSH key to be able to use it as a Rex Box.

For KVM boxes this cloud-init metadata can be provided as a cdrom device using an ISO image, which can be generated like so:

cloud-localds cidata.iso user-data.yaml

Describe the solution you would like

Have a $box->cloud_init() function which accepts a cloud-init user-data configuration in YAML format.

Also provide a minimal cloud-init configuration example to set up user rex with password box and enable passwordless sudo for that user.

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The instance-data feature of cloud-init is to be ignored.

Additional context

My fork contains an implementation of the cloud-init functionality in the feature/cloud-init-kvm branch (relevant commit: arpadszasz@5017f5a)