Create /orders/addtag end-point
Create /orders/addtag end-point

Probably not exactly within your coding style but is something I require so I thought, I might as well fork and offer a little push to continue. If I have time I might do some more methods, and also change the exposition on some others as your code isn't completely DRY.
501st-alpha1/ShipStation,RealTimeApps/ShipStation,ortega-io/ShipStation