Use real types to parse labels

We were using `yaml.Unmarshal` on basic types or inline structs. This
was not efficient and not clear to defined what we expect in labels.
We now use types to unmarshal the labels.

Only the `values` label is, at this time, parsed by GetValuesFromLabel
because this `utils` function is clearly a special case.

generator/labelStructs/secrets.go

@@ -0,0 +1,13 @@
+package labelStructs
+
+import "gopkg.in/yaml.v3"
+
+type Secrets []string
+
+func SecretsFrom(data string) (Secrets, error) {
+	var mapping Secrets
+	if err := yaml.Unmarshal([]byte(data), &mapping); err != nil {
+		return nil, err
+	}
+	return mapping, nil
+}