Support new CreateElementChildren endpoint

Depends #366 (closed)

Support the new CreateElementChildren endpoint, available in Arkindex 1.6.2 to create element paths in bulk. This will support batch publication.

Refs https://redmine.teklia.com/issues/8143

changed milestone to %0.4.0

added P2 label

assigned to @ebardou

changed the description

mentioned in merge request !573 (merged)

closed with merge request !573 (merged)