Add or update a batch of articles in one call. Unlike POST /locations-directory/articles, this endpoint does not create a new article every time: an article's identity here is the combination of its type_id and its set of linked LOCATION/SERVICE/STAFF entities (its "link tuple"), so re-submitting that same combination versions the existing article instead of creating a second one or failing with a conflict. It targets article types whose link patterns all have MULTIPLE cardinality — types with a SINGLE-cardinality pattern must be written through POST /locations-directory/articles instead, which enforces the "at most one live article per entity" rule this endpoint does not.

Applying a batch is all-or-nothing: if any article in articles fails validation, the whole batch is rejected with 422 Unprocessable Entity and nothing is written.

A version_token identifies one write run, and a run may span several calls to this endpoint when a source document has more than 100 articles — every call in the run must carry the same version_token, because POST /locations-directory/articles/rollback uses it to undo the run as a unit. Re-submitting a link tuple under a version_token that already wrote it is treated as retrying that exact write and is skipped, even if the submitted content differs — see version_token below for the full contract and the reason a fresh token must be minted per run.