REST API to add attachment on VBCS

Summary

We created a mobile app to approve Purchase Requisitions and POs and we want to add the 'Add attachment' function to our app.

Content

Hello guys,

Recently we created a mobile app using VBCS to approve Purchase Requisitions and Purchase Orders and we want to add the 'Add Attachment' function to our app. I've been searching on REST APIs to perform that task, since the "Perform Action on Task" REST API apparently doesn't have this feature, but I couldn't find anything on that.

Do you guys know if there's a REST API to add an attachment to the document or if there's any other way I can do that?