feat(datacopy): read environment variables (ConnectionStrings__* on server)

src/GreenHome.DataCopy/Program.cs

@@ -38,6 +38,7 @@ internal static class Program
         var config = new ConfigurationBuilder()
             .SetBasePath(AppContext.BaseDirectory)
             .AddJsonFile("appsettings.json")
+            .AddEnvironmentVariables() // lets the server pass ConnectionStrings__* env vars
             .Build();
 
         var sqlServerCs = config.GetConnectionString("SqlServer")