Add username to challenge csv export (#10956)

- Adds the member's username to the challenge csv
- Updates to unit tests
- Issue #10955

Supports the ability for challenge owners to judge challenge winners
after the added functionality enabling users to modify their name
(display name). The added field ties the user to their results by
their username.

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

@@ -577,7 +577,7 @@ api.exportChallengeCsv = {
         .lean().exec(),
     ]);
 
-    let resArray = members.map(member => [member._id, member.profile.name]);
+    let resArray = members.map(member => [member._id, member.profile.name, member.auth.local.username]);
 
     let lastUserId;
     let index = -1;
@@ -606,7 +606,7 @@ api.exportChallengeCsv = {
     let challengeTasks = _.reduce(challenge.tasksOrder.toObject(), (result, array) => {
       return result.concat(array);
     }, []).sort();
-    resArray.unshift(['UUID', 'name']);
+    resArray.unshift(['UUID', 'Display Name', 'Username']);
 
     _.times(challengeTasks.length, () => resArray[0].push('Task', 'Value', 'Notes', 'Streak'));