server/mw/oauth: res.loc.auth to true upon auth

Setting res.locals.authenticated explicity to
true makes it's more clear whether the req is
authenticated when using optionalAuthenticate
middlware.

server/middlewares/oauth.ts

@@ -20,6 +20,8 @@ function authenticate (req: express.Request, res: express.Response, next: expres
         .end()
     }
 
+    res.locals.authenticated = true
+
     return next()
   })
 }

server/tests/plugins/plugin-router.ts

@@ -53,7 +53,7 @@ describe('Test plugin helpers', function () {
         statusCodeExpected: 200
       })
 
-      expect(res.body.isAuthenticated).to.equal(undefined)
+      expect(res.body.isAuthenticated).to.equal(true)
 
       const secRes = await makeGetRequest({
         url: server.url,