saveUserInfo method
Implementation
Future<void> saveUserInfo(String firstName, String familyName,
String phonenumber, String accessToken) async {
_preferences = await SharedPreferences.getInstance();
_preferences.setString(first_name, firstName);
_preferences.setString(family_name, familyName);
_preferences.setString(preferred_username, phonenumber);
_preferences.setString(access_Token, accessToken);
}