List Entity Mappings

List every source-system to PaymentKit ID mapping for a migration. Returns the mappings created while the migration loaded data into PaymentKit, so you can resolve your original source IDs to PaymentKit IDs in bulk. Filter with `source_entity_type` to page one entity type at a time. Ordering is stable: rows sharing a `created_at` keep a deterministic relative order, so repeated calls at the same offset return the same rows. To page to completeness, pass `snapshot_at` and keep it constant across the whole run. Offset pagination is only consistent against a fixed row set — if the migration is still loading, newly created mappings enter the result set and shift the window, so a run without `snapshot_at` can miss or duplicate rows. With `snapshot_at` held constant, a full pass returns every mapping created at or before that instant exactly once, provided existing mappings are not deleted mid-run — the clamp bounds which rows enter the set, not which leave it.