Schema for Oanda guaranteed stop loss order parameters.
Oanda Docs
@type t() :: %ExOanda.GuaranteedStopLossOrderParameters{ mutability_market_halted: (:FIXED | :REPLACEABLE | :CANCELABLE | :PRICE_WIDEN_ONLY) | nil, mutability_market_open: (:FIXED | :REPLACEABLE | :CANCELABLE | :PRICE_WIDEN_ONLY) | nil }