PeopleSoft REST POST with Message Body

I'm trying to understand how to build a custom REST service to expose/insert/update data in PeopleSoft to other systems.

We understand how to build SOAP messages to expose data and are comfortable with configuring those.  We are also comfortable with REST GET.

We want to stop using SOAP and there are no clear examples, that we could find, of POST using REST in PeopleSoft.

I did find this one partial example in the community below:

&token = "accesstokenvalue";
&json_msg = "{";
&json_msg = &json_msg | """refresh_token"":""" | &token | """";
&json_msg = &json_msg | "}";
&request = CreateMessage(Operation.MY_TEST_POST, %IntBroker_Request);