Stop nested class parameters being parsed as classes

encapi's cobbler-wire document keys class parameters under the role name, and
the line-based parser treats every indented line as a class, so a node with
class params is classified with the parameter keys as extra classes.

- track the indentation of the classes block and skip deeper lines
- cover the nested form real cobbler-imported nodes return

parse_test.go

@@ -0,0 +1,53 @@
+package main
+
+import "testing"
+
+// Nodes imported from cobbler carry class parameters, which encapi emits as a
+// nested block under the role name. ausyd1nxvm2020/2021/2022 carry the role
+// name as its own class parameter, so a line-based parser that treats every
+// indented line as a class name emits the role twice.
+func TestParseClassesNestedBlockIsOneClass(t *testing.T) {
+	body := []byte("classes:\n" +
+		"    roles::infra::proxy::jumphost:\n" +
+		"        roles::infra::proxy::jumphost: '~'\n" +
+		"environment: develop\n" +
+		"parameters: {}\n")
+
+	doc, err := parseCobbler(body)
+	if err != nil {
+		t.Fatalf("parseCobbler returned error: %v", err)
+	}
+	want := []string{"roles::infra::proxy::jumphost"}
+	if len(doc.classes) != len(want) || doc.classes[0] != want[0] {
+		t.Errorf("classes = %q, want %q", doc.classes, want)
+	}
+	if doc.environment != "develop" {
+		t.Errorf("environment = %q, want develop", doc.environment)
+	}
+}
+
+// The same shape with ordinary class parameters: the parameter keys are values
+// of the class, never classes themselves.
+func TestParseClassesNestedParamsAreNotClasses(t *testing.T) {
+	body := []byte("classes:\n" +
+		"    roles::base:\n" +
+		"        listen_port: 8140\n" +
+		"        tls: true\n" +
+		"    roles::infra::dns::master: {}\n" +
+		"environment: production\n" +
+		"parameters: {}\n")
+
+	doc, err := parseCobbler(body)
+	if err != nil {
+		t.Fatalf("parseCobbler returned error: %v", err)
+	}
+	want := []string{"roles::base", "roles::infra::dns::master"}
+	if len(doc.classes) != len(want) {
+		t.Fatalf("classes = %q, want %q", doc.classes, want)
+	}
+	for i := range want {
+		if doc.classes[i] != want[i] {
+			t.Errorf("classes[%d] = %q, want %q", i, doc.classes[i], want[i])
+		}
+	}
+}