The post you linked is good, but it is unfortunately about creating an end-user app that shows data fetched from the API. I want to push data into Cayenne. This seems to be possible with cayenne-api-http-api-reference-api-things-sending-a-command-to-a-mqtt-channel-through-http-api
I wholeheartedly agree that the documentation isn’t great yet.
However, many of the bugs are covered in this thread: Integration of JSON data from HTTP/S API
I am currently working through the bugs one by one to try to get something working.
Hopefully this can save others some time.