See my project here as it may help you a bit: Raspberry Pi with PHP (or Arduino/ESP8266/NodeMCU) to GPIO to Relay to Gate/Garage Trigger
Also install Fiddler Tool and monitor your HTTP traffic while running some of the commands from the web browser. This is how I capture the device’s actions and attempt to talk to their internal API. In your case, it seems pretty simple. Just concentrate on the SENT headers and making sure that you replicate those in the Groovy/ST code. SENT panel is the top right of Fiddler while RECEIVED response panel is bottom right in Fiddler.