API method to publish a content item together with its one-level nested content — the non-shared, non-dynamic-page-list containers its `Content` fields point at (PROD-2489). A separate route rather than a flag on `item/{contentID}/publish` because the expansion can exceed one batch. Rather than refusing an oversized cascade, the work is split across several batches and every batchID is returned — the shape `ImportUrlRedirections` uses beside `SaveUrlRedirections`. `item/{contentID}/publish` is unchanged. As with every batch endpoint, this only enqueues: Classic enforces the caller's permission on each item when it processes the batch, so an item the caller cannot publish fails within its batch while the rest proceed.