ui: support pinnedFilter metadata (#650)

packages/ui-default/templates/partials/problem_search.html

@@ -1,16 +1,18 @@
-<div class="section__body search-container">
 {% set pinnedFilter = handler.domain.pinnedFilter|parseYaml %}
 {% set categories = (handler.domain.problemCategories or model.system.get('problem.categories'))|parseYaml %}
-{% for k, v in pinnedFilter %}
+<div class="section__body search-container">
+  {% for k, v in pinnedFilter %}
   <div class="flex-row flex-cross-center">
     <b class="title">{{ k }}: &nbsp;&nbsp;</b>
     <div class="chip-list flex-wrap flex-row" data-pinned-container>
       {%- for name, t in v -%}
-      <a class="chip-list__item search-tag__item" data-selection="{{ t }}">{{ name }}</a>
+        {% if name !== '__metadata__' %}
+        <a class="chip-list__item search-tag__item" data-selection="{{ t }}" {% if pinnedFilter[k]['__metadata__']['single'] %}data-filter="{{ k }}"{% endif %}>{{ name }}</a>
+        {% endif %}
       {%- endfor -%}
     </div>
   </div>
-{% endfor %} 
+  {% endfor %} 
   <div class="flex-row flex-cross-center">
     <b class="title">{{ _('Problem Category') }}: &nbsp;&nbsp;</b>
     <div class="chip-list flex-wrap flex-row">