Applies a flat list of UPSERT/DELETE operations across LOCATION, SERVICE, STAFF, and ARTICLE entities in one all-or-nothing transaction, with optional cross-entity links (e.g. a STAFF UPSERT linking to a LOCATION created earlier in the same call). Bridges the gap between the single-entity create/update/delete endpoints (one call per entity, no cross-type linking) and the CSV bulk-upload endpoint (one entity type per file, no linking to other types either): use this endpoint when a single caller-side change needs to touch several entities and/or types together and either all of it lands or none of it does.

Processing order. Two passes, not submission order: every UPSERT first (in dependency order LOCATION → SERVICE → STAFF → ARTICLE, so a links reference to an entity created earlier in the same batch always resolves), then every DELETE. The response still mirrors submission order — results[i] corresponds to operations[i] regardless of which pass actually applied it.

entity per operation + entity_type combination:

• UPSERT LOCATION — same fields as the single-entity location create/update request:
  name (required), external_id (optional — a random one is generated if omitted; matches
  an existing location to update it in place, otherwise creates a new one), type,
  image_url, phone_numbers (list of {phone_number, name}), time_zone (required, IANA
  id), address (required — {address, country_name, zip_code} required, plus region_name,
  city, coordinates: {latitude, longitude}), open_hours (list of
  {day_of_week, slots: [{open_at, close_at}]}), special_dates, custom_fields. Does not
  accept links.

• UPSERT SERVICE — service_name (required), description (required), external_id,
  service_type, duration, price, virtual_location_url, location_ids (internal
  location ids — not links; a SERVICE's location association is this field), open_hours,
  special_dates, phone_numbers, time_zone, custom_fields. Does not accept links.

• UPSERT STAFF — name (required), external_id, description, photo_url, status,
  gender, languages, job_title, contacts (list of {type, value, description}),
  manager, pronouns, specialities, date_of_birth, date_of_hire, attributes (free-form
  string map), relationships (list of {location_id, service_id}, by internal id — same as
  the single-entity staff endpoint), visit_types (list of {id, name}), tag_ids,
  custom_fields. Additionally accepts operation-level links to LOCATION and/or SERVICE (by
  external_id): a LOCATION link and a SERVICE link both present are paired (cross-product)
  into the staff's relationships; either alone is recorded with the other side unset.

• UPSERT ARTICLE — type_id (required — an existing article type's id), content
  (required — arbitrary JSON, validated against the type's schema when the type's content type
  is JSON), tags (list of strings). The batch's top-level source_key is required whenever
  any ARTICLE UPSERT is present. Accepts operation-level links to LOCATION, SERVICE, and/or
  STAFF (by external_id — an ARTICLE is never a valid link target); does not accept an
  embedded entity.links object (the single-article endpoint's
  shape) — use the operation-level links array instead. The article's type must currently be
  enabled for the account, and the type's declared link patterns must admit the combination of
  linked entity types submitted.

• DELETE (any entity_type) — entity is just { "id": "..." }. For LOCATION/SERVICE/
  STAFF, id is the external_id (the same identity UPSERT uses) — a value matching nothing
  is a silent no-op, still reported in the response. For ARTICLE, id is the internal id
  (articles have no external_id). DELETE does not accept links.

Validation rejects the whole batch (no operation applied) when: there are more than 100 operations; two UPSERTs of the same entity type share an external_id; a links entry (or a same-entity-type UPSERT) targets something a DELETE in this same batch also targets — applying every UPSERT before any DELETE makes that ordering unresolvable; a links entry resolves to neither another operation in the batch nor an existing account entity; an ARTICLE UPSERT carries an embedded entity.links; or any single operation fails its own field-level validation (reported as the first offending operations[i]).