add functionality

templates/admin/checked_in.html.twig

@@ -1,6 +1,7 @@
 {% if not field.value %}
-<button data-controller="checkin" data-id="">Einchecken</button>
-    {{ dump(field) }}
+    <form action="{{ path('admin_checkin', {'entityId': entityId(field)}) }}" method="post">
+        <button type="submit">Einchecken</button>
+    </form>
 {% else %}
-<button disabled>Eingechecked</button>
-{% endif %}
+<button disabled>Eingecheckt</button>
+{% endif %}