Show notice when migration affects tracking settings

[MAILPOET-3185]

lib/Util/Notices/ChangedTrackingNotice.php

@@ -0,0 +1,39 @@
+<?php
+
+namespace MailPoet\Util\Notices;
+
+use MailPoet\Util\Helpers;
+use MailPoet\WP\Functions as WPFunctions;
+use MailPoet\WP\Notice;
+
+class ChangedTrackingNotice {
+  const OPTION_NAME = 'mailpoet-changed-tracking-settings-notice';
+
+  /** @var WPFunctions */
+  private $wp;
+
+  public function __construct(
+    WPFunctions $wp
+  ) {
+    $this->wp = $wp;
+  }
+
+  public function init($shouldDisplay) {
+    if ($shouldDisplay && $this->wp->getTransient(self::OPTION_NAME)) {
+      return $this->display();
+    }
+    return null;
+  }
+
+  public function display() {
+    $text = __('Email open and click tracking is now enabled. You can change how MailPoet tracks your subscribers in [link]Settings[/link]', 'mailpoet');
+    $text = Helpers::replaceLinkTags($text, 'admin.php?page=mailpoet-settings#advanced');
+    $extraClasses = 'mailpoet-dismissible-notice is-dismissible';
+
+    return Notice::displayWarning($text, $extraClasses, self::OPTION_NAME);
+  }
+
+  public function disable() {
+    $this->wp->deleteTransient(self::OPTION_NAME);
+  }
+}