Create a dataset by importing history instead of uploading it

A second way to get data into a dataset, alongside POST /datasets: instead of PUTting a file yourself, ask the API to go fetch history on your behalf. Creates the dataset and starts the fetch in the same call — there is no separate upload step, and the result lands as a dataset version indistinguishable from an uploaded one once it's ready. Poll GET /datasets/{datasetId}/imports/{importId} for progress.

type selects the source. dex — history over a pool/pair's own on-chain market — is the only value today; other source types join this same endpoint later.

A dex import has two data shapes, chosen by the top-level cadence:

• Omitted/blank (default) — on-chain swap history, replayed directly from the pool/pair's own chain. Cadence is native, not resampled: each swap keeps the timestamp it happened at rather than being bucketed into candles, so the resulting version's cadence is rt unless the swaps happen to sit on a fixed grid (see DatasetVersion.cadence).
• One of 1s / 1m / 5m — pre-aggregated candles at that width instead of raw trades. The resulting dataset's type is klines, not ticker. Not every network supports every cadence yet — an unsupported combination fails asynchronously, same as an unresolvable pool (see the failed status on the poll endpoint below).