Stream-based cursor pagination helpers.
Usage
# Lazy stream — fetches pages on demand
Tink.Paginator.stream(fn page_token ->
Tink.Transactions.list_transactions(client, page_token: page_token, page_size: 100)
end, items_key: "transactions")
|> Stream.filter(&(&1["type"] == "DEBIT"))
|> Enum.take(500)