List the US Treasuries that fixed income requests trade and repo requests take as
collateral, ordered by maturity. Pass a treasury's cusip (or ISIN, or tokenId)
as instrument_id, or its CUSIP as cusip, on POST /api/rfq/requests.

By default only tradeable treasuries are listed: active, enabled for trading, and
maturing after today's New York date. cusip resolves one treasury exactly by CUSIP
or ISIN and takes precedence over q; it is tradeable-only too unless scope is
sent. Without limit every match is returned.

With asset_class=equity it lists the equities spot requests trade instead, ordered
by symbol. Pass an equity's tokenId or symbol as instrument_id on a spot
request. An equity carries only assetClass, tokenId, tokenAdmin, symbol and
name; tradeable means active and enabled for trading. Equities never mature, so
cusip and scope=expired are rejected. Listing equities requires the spot equity
board.