Is there a way to command my drone to fly to a geographic point, and then circle around it at a defined radius.
FlytOS has not implemented any such feature, but it would expose this if implemented by APM/PX4.
Please coordinate with APM/PX4 community to understand how to implement this.
Note: I am not sure, but for APM switching the vehicle to CIRCLE mode would solve your issue.
Moreover, you can use position_set or velocity_set APIs to move the drone in a circle.