Processing model from code

Hi all,

I created dataset on PPU workspace that contains deployed model with on-premise sources (model is deployed through C#  code, using TOM library).
Deploy went well, but I'm having problems with processing datasource.
I cannot find a way to create connection string to on-premise source.

Meanwhile, I created second model with the same on-premise datasource with PowerBI client and published on the PPU workspace.
when I click on Connection->Script Connection as-> Create To from SSMS, I get following script

{
"create": {
"parentObject": {
"database": "test_delete"
},
"dataSource": {
"name": "ea2de3af-dbac-44d4-bddc-52df729c086b",
"connectionString": "Provider=Microsoft.PowerBI.OleDb;Global Pipe=f26e04ac-4669-496b-b3a4-f313fe673cd1;Mashup=\"VERY_LONG_STRING\";Location=\"dim CustomerView\"",
"impersonationMode": "impersonateCurrentUser"
}
}
}

How can I connect to this datasource with my code?

I cannot find a way to create conenction string properly because I'm not familiar with "Global Pipe" and Mashup variables,
which PBI construct automatically.

I also checked PowerBI Api's (https://api.powerbi.com/v1.0/myorg/) on how to process PBI datasource from code, but cannot find any clue.

If I recap:
- I have installed and configured gateway properly
- I can connect to PBI workspace and deploy model from my code
- the problem is when I try to process analysis services from code because it points to on-premise datasource

I wonder if there is also another way to process model?

Thanks