core&ui: add new features about domain (#528)

Co-authored-by: undefined <i@undefined.moe>

- Add navigation hint
- Update homework/contest filter by assign
- Allow empty query for DomainSelectAutoComplete

packages/ui-default/templates/home_domain.html

@@ -33,6 +33,15 @@
             <img src="{{ avatarUrl(ddoc.avatar, 32) }}" width="32" height="32">
           </td>
           <td class="col--name">
+            <form class="form--inline" method="post">
+              <input type="hidden" name="id" value="{{ ddoc['_id'] }}">
+              {% set _show = handler.user.pinnedDomains.includes(ddoc._id) %}
+              <input type="hidden" name="operation" value="{{ "unstar" if _show else "star" }}">
+              <button class="star{% if _show %} activated{% endif %}" type="submit">
+                <span class="starred--hide"><span class="icon icon-star--outline" data-tooltip="{{ _('Star') }}"></span></span>
+                <span class="starred--show"><span class="icon icon-star" data-tooltip="{{ _('Unstar') }}"></span></span>
+              </button>
+            </form>
             {{ ddoc['name'] }} ({{ ddoc['_id'] }})
           </td>
           <td class="col--role">