Introduce backup and restore functionalities

[christian-roggia]

This PR introduces Velero for backup and restore functionalities and closes the ticket #6. NOTE: A daily and weekly schedule has been already created for automated backups, please refer to the documentation.

[clezag]

Thanks for the PR, already merged.

I tried to apply the changes to our new (new) infrastructure on Consip, that I'm currently in the process of testing. I got the following error:

aws_iam_role.velero_role: Creation complete after 0s [id=AmazonEKSVeleroRole]
╷
│ Error: creating Amazon S3 (Simple Storage) Bucket (velero-opendatahub-bfe86313): BucketAlreadyExists: The requested bucket name is not available. The bucket namespace is shared by all users of the system. Please select a different name and try again.
│       status code: 409, request id: WC2WEDAMAZ38XCAT, host id: 0HAO1eoIMcqUccZuF12QKzDP3fdNALzsbnqySVa/Orrz9Iw3erT/rT/RG9sqqJk6aP4Ytigw6bo=
│ 
│   with aws_s3_bucket.velero,
│   on velero.tf line 88, in resource "aws_s3_bucket" "velero":
│   88: resource "aws_s3_bucket" "velero" {
│ 

Is there a reason that the bucket name is hardcoded or could we randomize this?