Sitegen-Maven-Plugin: Maven properties are no longer resolved in sitegen.yaml

[ghillert]

It looks like in the 3.x versions, Maven properties are no longer resolved in sitegen.yaml. The following was working previously with the 2.x versions of the plugin:

engine:
  asciidoctor:
    images-dir: "./images"
    libraries:
      - "asciidoctor-diagram"
    attributes:
...
      version-coherence-maven: "${revision}"
      version-coherence-spring: "${project.version}"
      version-coherence: "${coherence.version}"
...

While the attribute itself, e.g. version-coherence-maven is set, the Maven property is not resolved but rather passed on as a string ${revision}.