Narrow down interfaces required in kustomize and kubectl helpers functions and provide `envtest` cluster wrapper to work with these

[pmalek]

Problem statement

KTF provides several functions which allow to interact with kubectl (and kustomize via kubetl -k) in

kubernetes-testing-framework/pkg/clusters/utils.go

Lines 211 to 239 in efb08ea

	// KustomizeDeployForCluster applies a given kustomizeURL to the provided cluster
	func KustomizeDeployForCluster(ctx context.Context, cluster Cluster, kustomizeURL string, flags ...string) error {
	return kubectlWithArgs(ctx, cluster, append([]string{"-v9", "apply", "-k", kustomizeURL}, flags...)...)
	}
	// KustomizeDeleteForCluster deletes the provided kustomize manafests from the cluster
	func KustomizeDeleteForCluster(ctx context.Context, cluster Cluster, kustomizeURL string, flags ...string) error {
	return kubectlWithArgs(ctx, cluster, append([]string{"-v9", "delete", "-k", kustomizeURL}, flags...)...)
	}
	// ApplyManifestByURL applies a given manifest URL to the cluster provided
	func ApplyManifestByURL(ctx context.Context, cluster Cluster, url string) error {
	return kubectlWithArgs(ctx, cluster, "apply", "-f", url)
	}
	// DeleteManifestByURL deletes a given manifest URL on the cluster provided
	func DeleteManifestByURL(ctx context.Context, cluster Cluster, url string) error {
	return kubectlWithArgs(ctx, cluster, "delete", "-f", url)
	}
	// ApplyManifestByYAML applies a given YAML manifest to the cluster provided
	func ApplyManifestByYAML(ctx context.Context, cluster Cluster, yaml string) error {
	return kubectlSubcommandWithYAML(ctx, cluster, "apply", yaml)
	}
	// DeleteManifestByYAML deletes a given YAML manifest on the cluster provided
	func DeleteManifestByYAML(ctx context.Context, cluster Cluster, yaml string) error {
	return kubectlSubcommandWithYAML(ctx, cluster, "delete", yaml)
	}

.

These functions access cluster.Cluster which is an interface with numerous methods which not all clusters might provide

In several projects like KIC or KGO, envtest is used to create clusters on the fly. These clusters are not yet supported.

This task tracks the effort to:

• narrow down the interface accepted by kustomize and kubectl helper funcs linked above
• provide a wrapper type for envtest so that these funcs can be utilized with envtest clusters

Acceptance criteria

• ktf kustomize and kubectl helpers funcs can be used with envtest clusters