Catch JWT expiration.

Closes #321

lib/www/server/api/middleware/auth/jwt.js

@@ -11,12 +11,27 @@ const getToken = function (req) {
 	return null;
 }
 
+const onExpired = async function (req, err) {
+	// If it's not too badly expired, let it through
+	// and hope that a new token will be issued soon.
+	const elapsed = new Date() - err.inner.expiredAt;
+	// TODO: Add proper logging
+	// console.log("Expiry details (elapsed, gracePeriod)", elapsed, cfg.gracePeriod*1000);
+	if (elapsed < cfg.gracePeriod*1000) {
+		// console.log("JWT within grace period");
+		return;
+	}
+
+	throw err;
+}
+
 const options = {
 	secret: cfg.secret,
 	credentialsRequired: false,
 	algorithms: ['HS256'],
 	requestProperty: "user",
-	getToken
+	getToken,
+	onExpired
 };
 
 module.exports = expressJWT(options);