fix: explode yaml anchors (#126)

* do not require code changes at several places

pkg/model/anchors_test.go

@@ -0,0 +1,35 @@
+package model
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"gopkg.in/yaml.v3"
+)
+
+func TestVerifyCycleIsInvalid(t *testing.T) {
+	var node yaml.Node
+	err := yaml.Unmarshal([]byte(`
+a: &a
+  ref: *b
+
+b: &b
+  ref: *a
+`), &node)
+	assert.Error(t, err)
+}
+
+func TestVerifyNilAliasError(t *testing.T) {
+	var node yaml.Node
+	err := yaml.Unmarshal([]byte(`
+test:
+- a
+- b
+- c`), &node)
+	*node.Content[0].Content[1].Content[1] = yaml.Node{
+		Kind: yaml.AliasNode,
+	}
+	assert.NoError(t, err)
+	err = resolveAliases(&node)
+	assert.Error(t, err)
+}