Using Apex for BPM task forms, using BPM REST API

We are trying to use APEX as a front end to Oracle BPM, rather than ADF but utilising the BPM REST API.

When using the BPM REST API is it possible to use authentication other than simple HTTP authentication when accessing the REST services?

We have OAM installed – is it possible to authenticate against the REST service using OAM and not simple authentication?

Alternatively is there an equivalent to the Java API call authenticateOnBehalfOf() in the REST API if we use a “static” admin user to authenticate against the REST service?

We are using BPM 12.1.3 and Apex version 18.1