AO3-3620 Fix subscriptions to other creator(s) for works co-authored with orphan_account

app/models/subscription.rb

@@ -37,13 +37,23 @@ def name
     end
   end
 
+  def creator_no_longer_associated_with?(creation)
+    return false unless subscribable_type == "User"
+
+    # If any of the creation's pseud's users matches the subscribable, then the
+    # creator still matches, so we return "true"
+    return false if creation.pseuds.any? { |p| p.user == subscribable }
+
+    # We reach this case if e.g. someone is subscribed to a user, but they
+    # orphan the work before the subscription notification would be sent
+    return true
+
   # Guard against scenarios that may break anonymity or other things.
   # Emails should only contain works or chapters.
   # Emails should only contain posted works or chapters.
   # Emails should never contain chapters of draft works.
   # Emails should never contain hidden works or chapters of hidden works.
-  # Emails should never contain orphaned works or chapters.
-  # TODO: AO3-3620 & AO3-5696: Allow subscriptions to orphan_account to receive notifications.
+  # Emails should not contain orphaned works or chapters if the subscription is to a creator no longer associated with the work
   # Emails for user subs should never contain anon works or chapters.
   # Emails for work subs should never contain anything but chapters.
   # TODO: AO3-1250: Anon series subscription improvements
@@ -52,7 +62,7 @@ def valid_notification_entry?(creation)
     return false unless creation.try(:posted)
     return false if creation.is_a?(Chapter) && !creation.work.try(:posted)
     return false if creation.try(:hidden_by_admin) || (creation.is_a?(Chapter) && creation.work.try(:hidden_by_admin))
-    return false if creation.pseuds.any? { |p| p.user == User.orphan_account }
+    return false if creator_no_longer_associated_with?(creation)
     return false if subscribable_type == "User" && creation.anonymous?
     return false if subscribable_type == "Work" && !creation.is_a?(Chapter)