Use `getSite()` instead of portal url

For the discussion controlpanel, change base URLs from portal URL to what getSite returns, but don't change the controlpanels context binding.
This allows for more flexibility when configuring it to be allowed on a sub site with a local registry.

CHANGES.rst

@@ -6,7 +6,9 @@ Changelog
 
 New:
 
-- *add item here*
+- For the discussion controlpanel, change base URLs from portal URL to what getSite returns, but don't change the controlpanels context binding.
+  This allows for more flexibility when configuring it to be allowed on a sub site with a local registry.
+  [thet]
 
 Fixes:
 

plone/app/discussion/browser/controlpanel.pt

@@ -22,7 +22,7 @@
             <tal:link i18n:name="label_mail_control_panel_link">
                 <a href=""
                    i18n:translate="text_no_mailhost_configured_control_panel_link"
-                   tal:attributes="href string:${portal_url}/@@mail-controlpanel"
+                   tal:attributes="href string:${view/site_url}/@@mail-controlpanel"
                 >Mail control panel</a>
             </tal:link>
             to fix this.
@@ -42,7 +42,7 @@
             <tal:link i18n:name="label_discussion_control_panel_link">
                 <a href=""
                    i18n:translate="text_discussion_type_control_panel_link"
-                   tal:attributes="href string:${portal_url}/@@content-controlpanel?type_id=Discussion Item"
+                   tal:attributes="href string:${view/site_url}/@@content-controlpanel?type_id=Discussion Item"
                 >Types control panel</a>
             </tal:link>
             to choose a workflow for the 'Discussion Item' type.
@@ -61,7 +61,7 @@
             <tal:link i18n:name="label_comments_migration_link">
                 <a href=""
                    i18n:translate="text_comments_migration_link"
-                   tal:attributes="href string:${portal_url}/@@comment-migration"
+                   tal:attributes="href string:${view/site_url}/@@comment-migration"
                 >migrate your comments</a>
             </tal:link>
             to fix this.
@@ -73,7 +73,7 @@
     </div>
 
     <a id="setup-link" class="link-parent"
-       tal:attributes="href string:$portal_url/@@overview-controlpanel"
+        tal:attributes="href string:${view/site_url}/@@overview-controlpanel"
         i18n:translate="">
       Site Setup
     </a>
@@ -87,7 +87,7 @@
     </div>
 
   <script type="text/javascript"
-          tal:attributes="src string:${context/portal_url}/++resource++plone.app.discussion.javascripts/controlpanel.js">
+          tal:attributes="src string:${portal_url}/++resource++plone.app.discussion.javascripts/controlpanel.js">
   </script>
 
 </article>

plone/app/discussion/browser/controlpanel.py

@@ -104,6 +104,13 @@ class DiscussionSettingsControlPanel(controlpanel.ControlPanelFormWrapper):
     form = DiscussionSettingsEditForm
     index = ViewPageTemplateFile('controlpanel.pt')
 
+    @property
+    def site_url(self):
+        """Return the absolute URL to the current site, which is likely not
+        necessarily the portal root.
+        """
+        return getSite().absolute_url()
+
     def settings(self):
         """Compose a string that contains all registry settings that are
            needed for the discussion control panel.