Add granular consent preference flow and regression tests

templates/components/cookie_banner.html

@@ -5,6 +5,21 @@
     <button type="submit" name="accept_all" value="1">Accept all</button>
     <button type="submit" name="reject_all" value="1">Reject all</button>
   </form>
+  <details>
+    <summary>Manage preferences</summary>
+    <form method="post" action="{% url 'consent' %}">
+      {% csrf_token %}
+      <label>
+        <input type="checkbox" name="analytics" value="1" />
+        Analytics cookies
+      </label>
+      <label>
+        <input type="checkbox" name="advertising" value="1" />
+        Advertising cookies
+      </label>
+      <button type="submit">Save preferences</button>
+    </form>
+  </details>
   {% if site_settings and site_settings.privacy_policy_page %}
     <a href="{{ site_settings.privacy_policy_page.url }}">Privacy Policy</a>
   {% endif %}