Migrate Almanac Device "mailKey" to modern storage

Summary: Ref T13065. See similar changes attached to that task.

Test Plan: Ran migration, got a clean database state, saw mail keys populate in mail property table.

Subscribers: PHID-OPKG-gm6ozazyms6q6i22gyam

Maniphest Tasks: T13065, T13641

Differential Revision: https://secure.phabricator.com/D21625

resources/sql/autopatches/20210316.almanac.01.device-mailkey.php

···
+<?php
+
+$device_table = new AlmanacDevice();
+$device_conn = $device_table->establishConnection('w');
+
+$properties_table = new PhabricatorMetaMTAMailProperties();
+$conn = $properties_table->establishConnection('w');
+
+$iterator = new LiskRawMigrationIterator(
+  $device_conn,
+  $device_table->getTableName());
+
+foreach ($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/20210316.almanac.02.device-dropmailkey.sql

···
+ALTER TABLE {$NAMESPACE}_almanac.almanac_device
+  DROP mailKey;

src/applications/almanac/storage/AlmanacDevice.php

···
 
   protected $name;
   protected $nameIndex;
-  protected $mailKey;
   protected $viewPolicy;
   protected $editPolicy;
   protected $isBoundToClusterService;
···
       self::CONFIG_COLUMN_SCHEMA => array(
         'name' => 'text128',
         'nameIndex' => 'bytes12',
-        'mailKey' => 'bytes20',
         'isBoundToClusterService' => 'bool',
       ),
       self::CONFIG_KEY_SCHEMA => array(
···
     AlmanacNames::validateName($this->getName());
 
     $this->nameIndex = PhabricatorHash::digestForIndex($this->getName());
-
-    if (!$this->mailKey) {
-      $this->mailKey = Filesystem::readRandomCharacters(20);
-    }
 
     return parent::save();
   }