Add a dto template to enable easier templating of DTOs.

The reason is to ensure less error-prone addition of required parameters and reduce chances incorrect JSON structure.

AT:
The macro should contain:

1. A type attribute (string, default: object)
2. A des attribute (string, default: empty)
3. A required attribute (list, default: empty list)
4. It should accept multiple property macro calls as nested content

Optional: Detect required properties through a Freemarker function