Import multiple check rules in one batch

Bulk variant of /api/import/check-rule. Atomically imports up to 1000 Prometheus alert rules into your organization with full editability — the resulting rules behave like UI-created assets, not API-managed ones, so they can be modified in the Dash0 UI afterwards. Intended for one-time migrations rather than ongoing Infrastructure-as-Code management.

Per-item id/origin resolution mirrors the single-rule import handler: items without an id receive a server-generated UUID; items with an id reuse it. Generated origins are not prefixed with api- and the rules remain UI-editable.

Behaves like the regular bulk endpoint in every other respect: items are validated up-front, the whole batch is rejected on any item failure, nothing is written on rollback, and the endpoint is not idempotent. This endpoint accepts request bodies up to 2 MB (vs. the 256 KB default for other endpoints) to accommodate batched payloads of up to 1000 rules per request.