Performance: My Challenges (#11065)

* use the same paging for "myChallenges" only loads 10 per call

* challenges: show loading above the load-more button (instead at the top)

* purple loading message and flat load-more button

* remove comment

* show loadMore button only when the request has 10 entries

* challenge card ui

website/server/controllers/api-v3/challenges.js

@@ -410,7 +410,7 @@ api.getUserChallenges = {
     // Instead of populate we make a find call manually because of https://github.com/Automattic/mongoose/issues/3833
     await Promise.all(resChals.map((chal, index) => {
       return Promise.all([
-        User.findById(chal.leader).select(nameFields).exec(),
+        User.findById(chal.leader).select(`${nameFields} backer contributor`).exec(),
         Group.findById(chal.group).select(basicGroupFields).exec(),
       ]).then(populatedData => {
         resChals[index].leader = populatedData[0] ? populatedData[0].toJSON({minimize: true}) : null;