def add_order_item id, project_id, quantity
      post_request "orders/#{id}/add_item", {order: {project_id: project_id, quantity: quantity}}
    end
def add_order_item id, project_id, quantity
      post_request "orders/#{id}/add_item", {order: {project_id: project_id, quantity: quantity}}
    end
Add a Project to an Order

 @param id
 @param project_id
 @param quantity