Policy - add destructible interface

Summary: Fixes T6957. If / when a policy object is destroyed, access to an object that uses that policy object is denied.

Test Plan: looked around in the code to fail confident enough to write the summary above

Reviewers: epriestley

Reviewed By: epriestley

Subscribers: Korvin, epriestley

Maniphest Tasks: T6957

Differential Revision: https://secure.phabricator.com/D11380

src/applications/policy/storage/PhabricatorPolicy.php

@@ -2,7 +2,9 @@
 
 final class PhabricatorPolicy
   extends PhabricatorPolicyDAO
-  implements PhabricatorPolicyInterface {
+  implements
+    PhabricatorPolicyInterface,
+    PhabricatorDestructibleInterface {
 
   const ACTION_ALLOW = 'allow';
   const ACTION_DENY = 'deny';
@@ -361,4 +363,15 @@ final class PhabricatorPolicy
     return null;
   }
 
+
+/* -(  PhabricatorDestructibleInterface  )----------------------------------- */
+
+
+  public function destroyObjectPermanently(
+    PhabricatorDestructionEngine $engine) {
+
+    $this->delete();
+  }
+
+
 }