Some of singletons paragraphs has mgnl:contentNode type. We should investigate if:

A] Those should have mgnl:component type.

• The counting of contentNodes in info.magnolia.pages.app.availability.CanAddComponentRule.isAvailableForItem(Item) should go away (Magnolia 5.x only).

B] Count contentNodes also in

• info.magnolia.templating.elements.AreaElement.numberOfComponents(Node)
• info.magnolia.templating.elements.AreaElement.end(Appendable)
• info.magnolia.templating.elements.AreaElement.hasComponents(Node) should call the numberOfComponents method to prevent code duplication.