Use username in challenge member dropdown (#11478)

* update challenge member dropdown and api to display and search by username rather than display name

* remove accidental whitespace

* fix api test

website/client/src/components/members/memberSearchDropdown.vue

@@ -19,7 +19,7 @@
       :key="member._id"
       @click="selectMember(member)"
     >
-      {{ member.profile.name }}
+      @{{ member.auth.local.username }}
     </b-dropdown-item>
   </b-dropdown>
 </template>

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

@@ -330,7 +330,7 @@ function _getMembersForItem (type) {
       }
 
       if (req.query.search) {
-        query['profile.name'] = { $regex: req.query.search };
+        query['auth.local.username'] = { $regex: req.query.search };
       }
     } else if (type === 'group-members') {
       if (group.type === 'guild') {