Allow Ponder questions and answers to be destroyed with bin/remove

Summary: Ref T5847.

Test Plan: Used `bin/remove destroy` to destroy a question. Saw the question and its answers get wiped out.

Reviewers: btrahan, shadowhand

Reviewed By: shadowhand

Subscribers: shadowhand, epriestley

Maniphest Tasks: T5847

Differential Revision: https://secure.phabricator.com/D10345

src/applications/ponder/storage/PonderAnswer.php

@@ -7,7 +7,8 @@ final class PonderAnswer extends PonderDAO
     PhabricatorPolicyInterface,
     PhabricatorFlaggableInterface,
     PhabricatorSubscribableInterface,
-    PhabricatorTokenReceiverInterface {
+    PhabricatorTokenReceiverInterface,
+    PhabricatorDestructibleInterface {
 
   const MARKUP_FIELD_CONTENT = 'markup:content';
 
@@ -195,4 +196,16 @@ final class PonderAnswer extends PonderDAO
     return true;
   }
 
+
+/* -(  PhabricatorDestructibleInterface  )----------------------------------- */
+
+
+  public function destroyObjectPermanently(
+    PhabricatorDestructionEngine $engine) {
+
+    $this->openTransaction();
+      $this->delete();
+    $this->saveTransaction();
+  }
+
 }

src/applications/ponder/storage/PonderQuestion.php

@@ -8,7 +8,8 @@ final class PonderQuestion extends PonderDAO
     PhabricatorFlaggableInterface,
     PhabricatorPolicyInterface,
     PhabricatorTokenReceiverInterface,
-    PhabricatorProjectInterface {
+    PhabricatorProjectInterface,
+    PhabricatorDestructibleInterface {
 
   const MARKUP_FIELD_CONTENT = 'markup:content';
 
@@ -247,4 +248,22 @@ final class PonderQuestion extends PonderDAO
     );
   }
 
+
+/* -(  PhabricatorDestructibleInterface  )----------------------------------- */
+
+  public function destroyObjectPermanently(
+    PhabricatorDestructionEngine $engine) {
+
+    $this->openTransaction();
+      $answers = id(new PonderAnswer())->loadAllWhere(
+        'questionID = %d',
+        $this->getID());
+      foreach ($answers as $answer) {
+        $engine->destroyObject($answer);
+      }
+
+      $this->delete();
+    $this->saveTransaction();
+  }
+
 }