- Prevents deleted newsletters from showing up in archives

- Adds a relationship to the sending queue table
- Resets hash on newsletter duplication and notification history creation
- Updates hash generation to use random string instead of newsletter id

lib/API/Endpoints/Newsletters.php

@@ -220,7 +220,9 @@ class Newsletters extends APIEndpoint {
       $newsletter->save();
       $subscriber = Subscriber::getCurrentWPUser();
       $preview_url = NewsletterUrl::getViewInBrowserUrl(
-        $data, $subscriber, $queue = false, $preview = true
+        NewsletterUrl::ACTION_EDITOR,
+        $newsletter,
+        $subscriber
       );
 
       return $this->successResponse(
@@ -339,7 +341,11 @@ class Newsletters extends APIEndpoint {
       // get preview url
       $subscriber = Subscriber::getCurrentWPUser();
       $newsletter->preview_url = NewsletterUrl::getViewInBrowserUrl(
-        $newsletter, $subscriber, $queue, $preview = true);
+        NewsletterUrl::ACTION_LISTING,
+        $newsletter,
+        $subscriber,
+        $queue
+      );
 
       $data[] = $newsletter->asArray();
     }