more FA5 stuff with small related refactoring

src/components/user_list_popover/user_list_popover.js

@@ -1,3 +1,9 @@
+import { library } from '@fortawesome/fontawesome-svg-core'
+import { faCircleNotch } from '@fortawesome/free-solid-svg-icons'
+
+library.add(
+  faCircleNotch
+)
 
 const UserListPopover = {
   name: 'UserListPopover',

src/components/user_list_popover/user_list_popover.vue

@@ -31,7 +31,7 @@
         </div>
       </div>
       <div v-else>
-        <i class="icon-spin4 animate-spin" />
+        <FAIcon icon="circle-notch" spin size="3x"/>
       </div>
     </div>
   </Popover>