Add outputs (attributes) to the akp_instance resource

[morey-tech]

Add outputs (attributes) to the akp_instance resource (example on a resource from another provider). This is most useful for the server URL used when connecting with the argocd CLI. This is useful when creating Terraform module outputs that indicate how to connect to the instance that was just created.

The current workaround is to build the URL from the subdomain.

  server_addr = "${akp_instance.argocd.argocd.spec.instance_spec.subdomain}.cd.akuity.cloud:443"

This would be improved if the resource had an attribute of server_url:

  server_addr = "${akp_instance.server_url}"