indicate articles that are targets of in-product links

kitsune/sumo/static/sumo/scss/components/_wiki.scss

@@ -3,6 +3,21 @@
 
 @import 'selectize/scss/selectize.default';
 
+#linked-in-product-indicator {
+  display: grid;
+  column-gap: 8px;
+  grid-template-columns: 24px 1fr;
+  margin-bottom: p.$spacing-xl;
+  img {
+    width: 24px;
+    height: 24px;
+  }
+  figcaption {
+    font-weight: bold;
+    line-height: normal;
+  }
+}
+
 #id_restrict_to_groups {
   // Prevents flickering by hiding the un-selectized select
   // until selectize uses it to make a new one that's visible.

kitsune/wiki/jinja2/wiki/document.html

@@ -57,6 +57,13 @@
     {{ search_box(settings, id='support-search-sidebar', params=search_params) }}
   </div>
 
+  {% if in_staff_group(user) and document.is_linked_in_product %}
+  <figure id="linked-in-product-indicator">
+    <img src="{{ webpack_static('sumo/img/info.svg') }}" alt="{{ _('information icon') }}" />
+    <figcaption>{{ _("Article is linked in product") }}</figcaption>
+  </figure>
+  {% endif %}
+
   {{ aaq_widget(request, "document") }}
 
   {% if fallback_reason == 'no_translation' %}

kitsune/wiki/models.py

@@ -19,6 +19,7 @@
 from pyquery import PyQuery
 
 from kitsune.gallery.models import Image
+from kitsune.inproduct.models import Redirect
 from kitsune.products.models import Product, Topic
 from kitsune.sumo.apps import ProgrammingError
 from kitsune.sumo.i18n import split_into_language_and_path
@@ -779,6 +780,17 @@ def is_unrestricted_for(self, user, use_cache=True):
 
         return user.id in self.unrestricted_for_user_ids
 
+    @cached_property
+    def is_linked_in_product(self):
+        if self.parent:
+            return Redirect.objects.filter(
+                (Q(locale__in=("", self.locale)) & Q(target__contains=f"kb/{self.parent.slug}"))
+                | (Q(locale=self.locale) & Q(target__contains=f"kb/{self.slug}"))
+            ).exists()
+        return Redirect.objects.filter(
+            locale__in=("", self.locale), target__contains=f"kb/{self.slug}"
+        ).exists()
+
 
 class AbstractRevision(models.Model):
     # **%(class)s** is being used because it will allow  a unique reverse name for the field