Support workflow sub-prototypes to be injected when creating a new document

When a new document (variant) is created via (folder) workflow, the document is created by copying a document prototype and then replace some values. The method that does this is

public String add(String category, String template, Map<String, String> arguments) throws WorkflowException, RepositoryException {

For Experience Pages, we want to support that when a prototype is used to create a new document (variant), that to this document variant, we can copy sub prototypes : Namely the hst:page layout for the Experience Page, also see CMS-13433 and CMS-13432 .

adouma and I discussed this and for now, came up with the following idea which is good of enough for now and if ever needed, we can add more generic support (though we could even still first allowed comma separated values)

In the

Map<String, String> arguments

map, we introduce two known keys, 1 key-value pair for specifying extra mixin which should go on the created variant and one key-value pair pointing to the UUID of the node that should be copied as-is (in case of XPage an hst:page containing the layout of the exp page)