'Returns the a unique identifier for the user
Returns None if there are no credentials.
The id is provided by the current credentials\' id_token.'

@property
def user_id(self):

    if (not self.credentials):
        return None
    try:
        return self.credentials.id_token['sub']
    except KeyError:
        current_app.logger.error('Invalid    id_token    {0}'.format(self.credentials.id_token))
