since IoT devices have limited storage, usually the metrics are dumped into another system like Prometheus. but that Prometheus data source used plotting cannot be used to control the device, which will have another endpoint and another API, so we need some kind of concept of data sinks. at least that's my idea right now, allow data links configured in the panels to poke some "data sink" with values that are available in the DataFrame or custom-entered into the UI, like we do with traceID for Exemplars, etc.