Example api module that processes POST without oauth

[f1-outsourcing]

Anybody know of a module that accepts a POST request on some REST endpoint like https://example.com/api/V1/processing/payment?

I have something working for 2.3.6, but I have problems with the 1.9. If there some example code / module, that would be nice.
Authentication with authkey in the header. Like to put an order to processed.