Template/Endpoints (Base)

* redo page render following the logic of:
      Response ─┬─> TextResponse ─> TextResponseImpl
                └─> TemplateResponse ─> TemplateResponseImpl
    * split up giant files, one per response path
    * caching becomes a trait, implemented where necessary
        * TextResponses (Ajax) can now be cached
    * make use of previously defined php classes for js objects
        * Tabs, Listview, Tooltip, Announcement, Markup, Book, ...
    * \Aowow\Template\PageTemplate is the new class to be cached
    * do not discard error messages generated after vars have been sent to template
      and store in session for display at a later time
    * implement tracking consent management
    * move logic out of template into their respective endpoints

includes/components/frontend/announcement.class.php

@@ -43,7 +43,7 @@ class Announcement implements \JsonSerializable
     public function jsonSerialize() : array
     {
         $json = array(
-            'parent' => 'announcement-' . abs($this->id),
+            'parent' => 'announcement-' . $this->id,
             'id'     => $this->editable ? -$this->id : $this->id,
             'mode'   => $this->mode,
             'status' => $this->status,