Minimal public HTTP executor for generated raw endpoint metadata.
@type transport() :: (method :: String.t(), url :: String.t(), headers :: [{String.t(), String.t()}], body :: binary() -> {:ok, non_neg_integer(), [{String.t(), String.t()}], binary()} | {:error, term()})
@spec fetch(Ccxt.RawEndpoint.t(), map() | keyword(), keyword()) :: {:ok, term()} | {:error, term()}
@spec request(Ccxt.RawEndpoint.t(), map() | keyword(), keyword()) :: {:ok, String.t(), [{String.t(), String.t()}], binary()} | {:error, term()}
@spec url(Ccxt.RawEndpoint.t(), map() | keyword(), keyword()) :: {:ok, String.t()} | {:error, term()}