Get help center collections. Returns only top-level collections by default; pass
parentId=<collectionId> to list the direct children of a collection, or parentId=all to list every
collection. Results are sorted by lexorank and each entry includes articlesCount and
subCollectionsCount. Note: this endpoint returns the dashboard view of a collection; project and
externalId are omitted. Use GET /helpcenter/collections/all for full documents. Pass site=<siteId> (or
site=default) to list one help center site's collections.
Bearer <token>.Ok