post https://example.com/api/v1/managed/orders/sell/market
Places a market order sell for a stock. This is the most common type of sell order, executing as soon as
possible (within US market hours). Minimum order value is $1, excluding fees. Stock prices may be subject to
change upon execution of the order.
More details on market orders here
Use the confirmation_code returned by this endpoint in the /order_requests endpoint to grab the order_id when available.