Validates that all necessary config parameters are specified.
        :type config: dict[str, dict[str, Any] | str]
        :param config: the module config

def _validate_config(self, config):
        """
        Validates that all necessary config parameters are specified.
        :type config: dict[str, dict[str, Any] | str]
        :param config: the module config
        """
        if config is None:
            raise ValueError("OIDCFrontend conf can't be 'None'.")

        for k in {"signing_key_path", "provider"}:
            if k not in config:
                raise ValueError("Missing configuration parameter '{}' for OpenID Connect frontend.".format(k))