add helper methods for authorization to Authenticator

app/Authenticator.js

@@ -25,6 +25,20 @@ class Authenticator {
     }
   };
 
+  withUser(req, res, callback) {
+    this.getAuthenticatedUser(req, (user) => {
+      if (user) callback(user);
+      else res.status(401).send({ code: 'auth error', message: 'user not logged in.' });
+    });
+  };
+
+  withAdmin(req, res, callback) {
+    this.withUser(req, res, (user) => {
+      if (user.role === 'Admin') callback(user)
+      else res.status(403).send({ code: 'auth error', message: 'user is not Admin.' });
+    });
+  };
+
 };
 
 module.exports = Authenticator;