Records API v2: write support

We've added write endpoints to version 2 of the records API, so you can now create, update, link, and delete records, and fully manage record types.

Building on the read endpoints we released a few weeks ago, "write" endpoints give you:

• Less response-handling logic. Writes return the record in the same shape a read does, errors follow one uniform structure, and you can reference fields by name or ID.

• Protection for live data. Use test_mode to work with test records, with an optional guardrail on updates and deletes that returns an error on a mode mismatch, so a staging job can't accidentally change live records.

• Safe retries. Send an idempotency-key on a create, and a retry after a timeout or dropped connection replays the original response instead of creating a duplicate.

To get started, check out the docs.