Graft takes a root node, a path to a role in root, byte array with an existing role and appends this role asa child of the role in root where the path specifies.

LinkChildrenToParents walks through the role tree and sets the correct parent for each child.

FIXME: workflowPath should be of type configuration.Path, not string.

RoleToYAML exists to avoid exporting aggregatorRole/iteratorRole.