Wierd issues in the WinUI3 / WebView2: Solving the User-Agent problem

TL/DR: To verify that you are setting the right user-agent, you have to check the "web resource requested" event's copy of the request headers, not the "navigation starting" event's copy. And you need to call AddWebResourceRequestedFilter. Background: why am I setting the user-agent, and why do I need to check it? I'm writing a simple app to parse NMEA data from a small GPS tracker (because that's…