Allow clusterctl to specify a custom Workload Cluster template

[aaroniscode]

User Story

As an operator I would like to be able to choose between multiple Workload Cluster templates when using clusterctl to create a new Workload Cluster. I might do this for a few reasons:

• Test different configurations. For example a CAPA cluster template designed to use Calico CNI and another CAPA cluster template designed to use VPC CNI.
• Test a configuration change, like adding Audit configuration to the KubeadmConfig

Detailed Description

As an operator I would like to store my Workload Cluster templates in source control, like GitHub. When deploying a cluster using clusterctl I'd like to be able to choose the template, like:

clusterctl config cluster dev --source=https://github.com/aaroniscode/capi-templates/capa-vpc-cni.yaml

Might also want to be able to use a local file

clusterctl config cluster dev --source=~/templates/capa-vpc-cni.yaml

/kind feature
/area clusterctl

[aaroniscode]

Some additional notes:

As @Arvinderpal pointed out in Slack, the --flavor flag could be used to point to different templates if the source could be changed to a different Github repository, and one where you don't have the requirement to publish a release.

Also when the filesystem backed is merged #1963, having the option to use a local template on the filesystem would be a good option to have.

[ncdc]

/help

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[fabriziopandini]

/lifecycle active
As per various discussions, including also:

• read templates from ConfigMap
• allow listing variables required by a workload cluster template