setUserProperty method
User properties are attributes you define to describe segments of your user base, such as language preference or geographic location. These can be used to define audiences for your app. See https://firebase.google.com/docs/analytics/user-properties?platform=android
Implementation
@override
void setUserProperty(String key, String value)
{
logInfo((_isEnabled ? 'GoogleAnalytics' : 'Disabled-GoogleAnalytics') + ': setUserProperty: key=$key value=$value');
if (_isEnabled)
_firebaseAnalytics.setUserProperty(name: key, value: value);
}