indicate articles that are targets of in-product links

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

@@ -3,6 +3,24 @@
 
 @import 'selectize/scss/selectize.default';
 
+figure {
+  &.linked-in-product {
+    display: flex;
+    margin-bottom: p.$spacing-xl;
+
+    img {
+      width: 24px;
+      height: 24px;
+      margin-right: p.$spacing-sm;
+    }
+
+    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/includes/sidebar_modules.html

@@ -6,6 +6,14 @@
   {% endif %}
   <nav id="doc-tools">
     <ul class="sidebar-nav sidebar-folding">
+      {% if in_staff_group(user) and (document or parent).is_linked_in_product %}
+        <li>
+          <figure class="linked-in-product">
+            <img src="{{ webpack_static('sumo/img/info.svg') }}" alt="{{ _('Information icon') }}" />
+            <figcaption>{{ _("Article is linked in product") }}</figcaption>
+          </figure>
+        </li>
+      {% endif %}
       <li id="editing-tools-sidebar">
         {% if user.is_authenticated %}
           <h3 class="sidebar-subheading large-only">{{ _('Editing Tools') }}</h3>

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