feat(bootstrap): add validation for harvester_kubeconfig_path when manage_storage_network is true

Summary

When manage_storage_network = true, the null_resource.storage_network provisioner relies on KUBECONFIG being set to var.harvester_kubeconfig_path. There is currently no validation ensuring this variable is non-empty, which will cause kubectl to fail silently or with an unhelpful error.

Required Change

Add a check block (or a precondition) in modules/bootstrap/main.tf to enforce that harvester_kubeconfig_path is non-empty whenever manage_storage_network = true. Example:

check "storage_network_kubeconfig_required" {
  assert {
    condition     = !var.manage_storage_network || var.harvester_kubeconfig_path != ""
    error_message = "harvester_kubeconfig_path is required when manage_storage_network = true."
  }
}

Context

• Identified in PR #84 (comment: https://github.com/wso2/open-cloud-datacenter/pull/84#discussion_r3167420908)
• File: modules/bootstrap/main.tf, null_resource.storage_network resource
• Variables involved: var.manage_storage_network, var.harvester_kubeconfig_path

References

• PR: https://github.com/wso2/open-cloud-datacenter/pull/84
• Requested by: @HiranAdikari

Start in modules/bootstrap/main.tf by reading the null_resource.storage_network resource and the definitions of manage_storage_network and harvester_kubeconfig_path. Confirm that an enabled storage network with an empty kubeconfig path fails validation, while disabled management and non-empty values remain valid, then run Terraform validation.