Add ID to Like and Undo

classes/Activitypub_like.php

@@ -55,6 +55,7 @@ class Activitypub_like extends Managed_DataObject
                     'https://www.w3.org/ns/activitystreams',
                     'https://w3id.org/security/v1'
             ],
+            'id'     => common_root_url().'like_from_'.urlencode($actor).'_to_'.urlencode($object),
             "type"   => "Like",
             "actor"  => $actor,
             "object" => $object

classes/Activitypub_undo.php

@@ -49,11 +49,16 @@ class Activitypub_undo extends Managed_DataObject
      */
     public static function undo_to_array($object)
     {
-        $res = array("@context" => "https://www.w3.org/ns/activitystreams",
-                          "type"   => "Undo",
-                          "actor"  => $object["actor"],
-                          "object" => $object
-                       );
+        $res = [
+            '@context' => [
+                    'https://www.w3.org/ns/activitystreams',
+                    'https://w3id.org/security/v1'
+            ],
+            'id'     => $object['id'].'/undo',
+            'type'   => 'Undo',
+            'actor'  => $object['actor'],
+            'object' => $object
+        ];
         return $res;
     }
 }