Use DestructionEngine to destroy UserEmail objects

Summary: Ref T13444. Prepare to hook identity updates when user email addreses are destroyed.

Test Plan:
  - Destroyed a user with `bin/remove destroy ... --trace`, saw email deleted.
  - Destroyed an email from the web UI, saw email deleted.

Maniphest Tasks: T13444

Differential Revision: https://secure.phabricator.com/D20912

src/__phutil_library_map__.php

@@ -11681,7 +11681,10 @@ phutil_register_library_map(array(
     'PhabricatorUserEditEngine' => 'PhabricatorEditEngine',
     'PhabricatorUserEditor' => 'PhabricatorEditor',
     'PhabricatorUserEditorTestCase' => 'PhabricatorTestCase',
-    'PhabricatorUserEmail' => 'PhabricatorUserDAO',
+    'PhabricatorUserEmail' => array(
+      'PhabricatorUserDAO',
+      'PhabricatorDestructibleInterface',
+    ),
     'PhabricatorUserEmailTestCase' => 'PhabricatorTestCase',
     'PhabricatorUserEmpowerTransaction' => 'PhabricatorUserTransactionType',
     'PhabricatorUserFerretEngine' => 'PhabricatorFerretEngine',

src/applications/people/editor/PhabricatorUserEditor.php

@@ -241,7 +241,8 @@ final class PhabricatorUserEditor extends PhabricatorEditor {
           throw new Exception(pht('Email not owned by user!'));
         }
 
-        $email->delete();
+        id(new PhabricatorDestructionEngine())
+          ->destroyObject($email);
 
         $log = PhabricatorUserLog::initializeNewLog(
           $actor,

src/applications/people/storage/PhabricatorUser.php

@@ -1148,7 +1148,7 @@ final class PhabricatorUser
         'userPHID = %s',
         $this->getPHID());
       foreach ($emails as $email) {
-        $email->delete();
+        $engine->destroyObject($email);
       }
 
       $sessions = id(new PhabricatorAuthSession())->loadAllWhere(

src/applications/people/storage/PhabricatorUserEmail.php

@@ -4,7 +4,9 @@
  * @task restrictions   Domain Restrictions
  * @task email          Email About Email
  */
-final class PhabricatorUserEmail extends PhabricatorUserDAO {
+final class PhabricatorUserEmail
+  extends PhabricatorUserDAO
+  implements PhabricatorDestructibleInterface {
 
   protected $userPHID;
   protected $address;
@@ -271,4 +273,13 @@ final class PhabricatorUserEmail extends PhabricatorUserDAO {
     return $this;
   }
 
+
+/* -(  PhabricatorDestructibleInterface  )----------------------------------- */
+
+
+  public function destroyObjectPermanently(
+    PhabricatorDestructionEngine $engine) {
+    $this->delete();
+  }
+
 }