Adding a table to a dataset with a datasource via v2 apis

Hi there, 

We currently have a dataset of base tables that we copy for each client and connect to their database for our embedded functionality, but some clients have custom tables that we'd like to add to their dynamically.  These tables can be different per client. 

Is there a way to do this programatically using the (v2) apis? 

I've been exploring using Datasets.PutTableInGroupAsync , but there's almost no doco on how to use this, especially how to structure requestMessage object.  Even if I got this to work, would it then grab data from the corresponding datasource during 

a refresh or would it be just a table on its own? 

If not does anyone know how to add a table that exists in the datasource to the power bi dataset programatically? 

Thanks in advance.