Expose transaction PHID in maniphest.gettasktransactions

Summary: Fixes T6629.

Test Plan: {F238271}

Reviewers: btrahan, chad, 20after4

Reviewed By: 20after4

Subscribers: 20after4, epriestley

Maniphest Tasks: T6629

Differential Revision: https://secure.phabricator.com/D10898

src/applications/maniphest/conduit/ManiphestGetTaskTransactionsConduitAPIMethod.php

@@ -64,6 +64,7 @@ final class ManiphestGetTaskTransactionsConduitAPIMethod
 
       $results[$task_id][] = array(
         'taskID'  => $task_id,
+        'transactionPHID' => $transaction->getPHID(),
         'transactionType'  => $transaction->getTransactionType(),
         'oldValue'  => $transaction->getOldValue(),
         'newValue'  => $transaction->getNewValue(),