Add cloud init support

[jbriard]

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Description

Add the option of sending data in the “user_data_file” to be able to run cloud init scripts during deployment.

Use Case(s)

The use case is to simplify the deployement and use a more powerfull tool to customize the VM

Potential configuration

"builders": [
{
"project_id": "{{ user project_id }}",
"access_key": "{{ user access_key }}",
"secret_key": "{{ user secret_key }}",
"server_name": "server",
"image_name": "server-apache",
"snapshot_name": "server-apache-snapshot",
"type": "scaleway",
(..)
"user_data_file": "/path/to/cloud-init-config.yaml"

}

],

Potential References