Wikimedia's User-Agent policy asks clients to send contact information in the User-Agent header, but MediaWiki itself does not generally do that. This is problematic for third party MediaWiki installations calling back to Wikimedia. But more generally, we should follow our own advice.

HttpRequestFactory::getUserAgent() should be updated to include contact info based on the canonical server URL, like ForeignAPIRepo::getUserAgent() does. Alternatively, we could use the EmergencyContact setting. It should also be possible to override the User-Agent entirely using a config setting.