Returns the DCM Floodlight session id, generating a new one if there's not already one

@returns {String} The session id
function floodlightSessionId() {
	const cookies = cookie.parse( document.cookie );

	const existingSessionId = cookies[ DCM_FLOODLIGHT_SESSION_COOKIE_NAME ];
	if ( existingSessionId ) {
		debug( 'Floodlight: Existing session: ' + existingSessionId );
		return existingSessionId;
	}

	// Generate a 32-byte random session id
	const newSessionId = uuid().replace( new RegExp( '-', 'g' ), '' );
	debug( 'Floodlight: New session: ' + newSessionId );
	return newSessionId;
}