Custom user agent in Akregator

I’m looking for a way to change the HTTP user-agent that Akregator uses when fetching feeds. I see in feedretriever.cpp that there is a “Custom user agent” setting, but it’s not exposed in the UI and I’m not sure where to put it in a config file. Can someone help me out?

I want to do this because Akregator’s default user agent makes me stand out a lot to small feeds, so it’s a privacy issue.