You can now use environment variables in project files. No need to use passwords in plain text. More details about that can be found here:
TLDR: You can define an environment variable and use it in data source definitions like this:
Data Sources: - Provider: SqlServer@1 Connection String: '%EnvironmentVariableName%' Name: DWH
Replacing environment variables works when you are reading data sources (but not tests!) from any provider.
Added a new how-to guide, see above. More will follow.