Set data source credentials on Power BI Report Server through REST API to create a scheduled refresh

I've just done some tests and the following payload worked for me doing a PATCH http request against http://localhost/Reports/api/v2.0/PowerBIReports( {id} )/DataSources. Note I've changed the CredentialRetrieval value to "store" and I found I had to add the username and password both in the CredentialsInServer object and as the username/secret in the DataModelDataSource (if I did not so this second bit the scheduled refresh would not work). I've also stripped out the creation and modification fields as I don't think you can alter those from the client side anyway.

[
    {
        "Id": "dcf1ca8d-4320-e911-bbac-94b86df86523",
        "Name": null,
        "Description": null,
        "Hidden": false,
        "Path": "",
        "IsEnabled": true,
        "DataSourceSubType": "DataModel",
        "DataModelDataSource": {
            "Type": "Import",
            "Kind": "SQL",
            "AuthType": "Windows",
            "SupportedAuthTypes": [
                "Windows",
                "UsernamePassword"
            ],
            "Username": "domain\\user",
            "Secret": "MyPassword",
            "ModelConnectionName": ""
        },
        "IsReference": false,
        "DataSourceType": "SQL",
        "ConnectionString": "localhost\\sql17;AdventureWorksDW2017",
        "IsConnectionStringOverridden": true,
        "CredentialRetrieval": "store",
        "CredentialsInServer": {
            "UserName": "domain\\user",
            "Password": "MyPassword",
            "UseAsWindowsCredentials": true,
            "ImpersonateAuthenticatedUser": false
        },
        "CredentialsByUser": null
        
    }
]