Allow Legalpad documents to be destroyed with bin/remove destroy

Summary: Ref T3116. Support permanent destruction of legal document objects.

Test Plan: Ran `bin/remove destroy L1`, saw it clean up the document body, signatures, transactions and edges.

Reviewers: btrahan, chad

Reviewed By: chad

Subscribers: epriestley

Maniphest Tasks: T3116

Differential Revision: https://secure.phabricator.com/D9775

src/__phutil_library_map__.php

@@ -3611,6 +3611,7 @@ phutil_register_library_map(array(
       1 => 'PhabricatorPolicyInterface',
       2 => 'PhabricatorSubscribableInterface',
       3 => 'PhabricatorApplicationTransactionInterface',
+      4 => 'PhabricatorDestructableInterface',
     ),
     'LegalpadDocumentBody' =>
     array(

src/applications/legalpad/storage/LegalpadDocument.php

@@ -4,7 +4,8 @@ final class LegalpadDocument extends LegalpadDAO
   implements
     PhabricatorPolicyInterface,
     PhabricatorSubscribableInterface,
-    PhabricatorApplicationTransactionInterface {
+    PhabricatorApplicationTransactionInterface,
+    PhabricatorDestructableInterface {
 
   protected $title;
   protected $contributorCount;
@@ -170,4 +171,31 @@ final class LegalpadDocument extends LegalpadDAO
     return new LegalpadTransaction();
   }
 
+
+/* -(  PhabricatorDestructableInterface  )----------------------------------- */
+
+
+  public function destroyObjectPermanently(
+    PhabricatorDestructionEngine $engine) {
+
+    $this->openTransaction();
+      $this->delete();
+
+      $bodies = id(new LegalpadDocumentBody())->loadAllWhere(
+        'documentPHID = %s',
+        $this->getPHID());
+      foreach ($bodies as $body) {
+        $body->delete();
+      }
+
+      $signatures = id(new LegalpadDocumentSignature())->loadAllWhere(
+        'documentPHID = %s',
+        $this->getPHID());
+      foreach ($signatures as $signature) {
+        $signature->delete();
+      }
+
+    $this->saveTransaction();
+  }
+
 }