KAZOO-3116 initial

Callback feature
Like I said earlier, calling other applications' modules is a no-no. This should be a wapi_offnet request to stepswitch to do the bridging. You are basically re-implementing the code in stepswtich, but probably missing corner cases or features expected when going to offnet resources.

If you really need to manually do the bridging here, you can create a new api function in wapi_offnet to return the endpoints (basically wrapping `stepswitch_resources:endpoints/2` in an API call). But ideally you would just publish the wapi_offnet API payload and listen for the responses.