gastro: change diet filter to a twig template

gastro.yaml

@@ -213,11 +213,13 @@ filter:
     name: |
       {{ keyTrans('diet') }}
     type: select
-    values:
-      '*':
-        name: |
-          {{ repoTrans('Objects with diet information') }}
-        query: nwr[~"^diet:"~"."]
+    values: |
+      <option weight='-1' value='*' query='nwr[~"^diet:"~"."]'>{{ repoTrans('Objects with diet information') }}</option>
+      {% for key, def in const.diet %}
+        <option value='{{ key }}' query='nwr["{{ key }}"]'>{{ keyTrans(key) }}</option>
+      {% endfor %}
+const:
+  diet:
     diet:vegan: {}
     diet:vegetarian: {}
     diet:pescetarian: {}
@@ -230,6 +232,3 @@ filter:
     diet:lactose_free: {}
     diet:halal: {}
     diet:kosher: {}
-    valueName: |
-      {{ keyTrans(value) }}
-    op: has_key_value