Implement DNS control (enable/disable blocking, possibly with a given timeout)

Signed-off-by: DL6ER <dl6er@dl6er.de>

scripts/pi-hole/js/groups-common.js

@@ -5,6 +5,8 @@
  *  This file is copyright under the latest version of the EUPL.
  *  Please see LICENSE file for your rights under this license. */
 
+/* global apiFailure:false */
+
 // eslint-disable-next-line no-unused-vars
 var groups = [];
 
@@ -17,5 +19,8 @@ function getGroups() {
     success: function (data) {
       groups = data.groups;
     },
+    error: function (data) {
+      apiFailure(data);
+    },
   });
 }