Add pure template-resolution logic (kctl.ResolveTemplate) with unit tests

internal/kctl/template_test.go

@@ -0,0 +1,41 @@
+package kctl
+
+import "testing"
+
+func TestResolveTemplate_SinglePlaceholder(t *testing.T) {
+	got := ResolveTemplate("secret-{namespace}", map[string]string{"namespace": "example-ns"})
+	want := "secret-example-ns"
+	if got != want {
+		t.Fatalf("got %q, want %q", got, want)
+	}
+}
+
+func TestResolveTemplate_MultiplePlaceholders(t *testing.T) {
+	template := "arn:aws:eks:{region}:{account_id}:cluster/tf-{env}-{context}-1"
+	values := map[string]string{
+		"region":     "eu-central-1",
+		"account_id": "123456789012",
+		"env":        "beta",
+		"context":    "internal",
+	}
+	got := ResolveTemplate(template, values)
+	want := "arn:aws:eks:eu-central-1:123456789012:cluster/tf-beta-internal-1"
+	if got != want {
+		t.Fatalf("got %q, want %q", got, want)
+	}
+}
+
+func TestResolveTemplate_UnknownPlaceholderLeftAsIs(t *testing.T) {
+	got := ResolveTemplate("secret-{unknown}", map[string]string{"namespace": "example-ns"})
+	want := "secret-{unknown}"
+	if got != want {
+		t.Fatalf("got %q, want %q", got, want)
+	}
+}
+
+func TestResolveTemplate_EmptyTemplate(t *testing.T) {
+	got := ResolveTemplate("", map[string]string{"namespace": "example-ns"})
+	if got != "" {
+		t.Fatalf("expected empty result, got %q", got)
+	}
+}