Hello Paul,
Rest API in Standard ERP only supports READ function. Writing for now is restricted.
Oauth is supported in Rest API at the moment.
More about Oauth is here:
https://hansaworld-web.s3.amazonaws.com/university/university/Webinars/2018/HW%20web%20api%20and%20Oauth2%20with%20standard-id.mp4
Best Regards,
Hansaworld