Gateway IDs when no gateway is set up

Thanks lbendlin for the link. The endpoint you've shared seems to be deprecated, but it's replacements Datasets - Update Datasources and Datasets - Update Datasources In Group commands would be able to update datasets.

However I've created the datasets using the Power BI XMLA endpoint. This makes the datasets incompatible with those endpoints. The Gateways - Update Datasource endpoint does not have this limitation, so I've been trying to use that. 

I've been able to find the hidden gateway ID by reading metadata from a dataset object when getting all datasets. Ideally there'd be a nicer way to find it though