logout method
Logs out the current session and go to the Routes.auth page.
Implementation
void logout() {
// Don't allow user to keep his profile, when no recovery methods are
// available or any password set, as they won't be able to sign in.
_authService.logout(canRecover || hasPassword.value ? keep.value : false);
router.auth();
router.tab = HomeTab.chats;
}