Migrate "SlowvotePoll" to modern mailkey storage

Summary:
Ref T13682. Ref T13065. Migrate and update "SlowvotePoll" to use more modern mailkey storage (in the mail application, rather than onboard).

Also make other minor modernization changes.

Test Plan: Created a new poll. Ran migration, verified mail key copied properly in database.

Subscribers: PHID-OPKG-gm6ozazyms6q6i22gyam

Maniphest Tasks: T13682, T13065

Differential Revision: https://secure.phabricator.com/D21842

resources/sql/autopatches/20220525.slowvote.01.mailkey.php

@@ -0,0 +1,28 @@
+<?php
+
+$poll_table = new PhabricatorSlowvotePoll();
+$poll_conn = $poll_table->establishConnection('w');
+
+$properties_table = new PhabricatorMetaMTAMailProperties();
+$conn = $properties_table->establishConnection('w');
+
+$iterator = new LiskRawMigrationIterator(
+  $poll_conn,
+  $poll_table->getTableName());
+
+foreach ($iterator as $row) {
+  queryfx(
+    $conn,
+    'INSERT IGNORE INTO %R
+        (objectPHID, mailProperties, dateCreated, dateModified)
+      VALUES
+        (%s, %s, %d, %d)',
+    $properties_table,
+    $row['phid'],
+    phutil_json_encode(
+      array(
+        'mailKey' => $row['mailKey'],
+      )),
+    PhabricatorTime::getNow(),
+    PhabricatorTime::getNow());
+}

resources/sql/autopatches/20220525.slowvote.02.mailkey-drop.sql

@@ -0,0 +1,2 @@
+ALTER TABLE {$NAMESPACE}_slowvote.slowvote_poll
+  DROP mailKey;

src/applications/slowvote/storage/PhabricatorSlowvotePoll.php

@@ -1,6 +1,7 @@
 <?php
 
-final class PhabricatorSlowvotePoll extends PhabricatorSlowvoteDAO
+final class PhabricatorSlowvotePoll
+  extends PhabricatorSlowvoteDAO
   implements
     PhabricatorApplicationTransactionInterface,
     PhabricatorPolicyInterface,
@@ -25,7 +26,6 @@ final class PhabricatorSlowvotePoll extends PhabricatorSlowvoteDAO
   protected $responseVisibility = 0;
   protected $shuffle = 0;
   protected $method;
-  protected $mailKey;
   protected $viewPolicy;
   protected $isClosed = 0;
   protected $spacePHID;
@@ -59,16 +59,14 @@ final class PhabricatorSlowvotePoll extends PhabricatorSlowvoteDAO
         'method' => 'uint32',
         'description' => 'text',
         'isClosed' => 'bool',
-        'mailKey' => 'bytes20',
       ),
       self::CONFIG_KEY_SCHEMA => array(
       ),
     ) + parent::getConfiguration();
   }
 
-  public function generatePHID() {
+  public function getPHIDType() {
-    return PhabricatorPHID::generateNewPHID(
+    return PhabricatorSlowvotePollPHIDType::TYPECONST;
-      PhabricatorSlowvotePollPHIDType::TYPECONST);
   }
 
   public function getOptions() {
@@ -112,13 +110,6 @@ final class PhabricatorSlowvotePoll extends PhabricatorSlowvoteDAO
     return '/'.$this->getMonogram();
   }
 
-  public function save() {
-    if (!$this->getMailKey()) {
-      $this->setMailKey(Filesystem::readRandomCharacters(20));
-    }
-    return parent::save();
-  }
-
 
 /* -(  PhabricatorApplicationTransactionInterface  )------------------------- */