[B] Allow creators to be optional

api/app/models/concerns/tracked_creator.rb

@@ -3,7 +3,7 @@ module TrackedCreator
   extend ActiveSupport::Concern
 
   included do
-    belongs_to :creator, class_name: "User", foreign_key: "creator_id"
+    belongs_to :creator, class_name: "User", foreign_key: "creator_id", optional: true
 
     delegate :name, to: :creator, prefix: true
   end

api/app/serializers/v1/annotation_serializer.rb

@@ -37,7 +37,7 @@ class AnnotationSerializer < ManifoldSerializer
       anonymous?(object, params)
     end
     typed_attribute :creator_name, Types::String.meta(read_only: true) do |object, params|
-      next object.creator.full_name if creator_identity_visible?(object, params)
+      next object.creator&.full_name if creator_identity_visible?(object, params)
 
       object.anonymous_label
     end

api/app/services/notifications/fetch_users_for_comment_notification.rb

@@ -20,7 +20,7 @@ def execute
 
     def excluded
       @excluded ||= [creator].tap do |out|
-        out << parent.creator if parent.present?
+        out << parent.creator if parent&.creator.present?
       end.compact
     end
   end

api/app/services/notifications/fetch_users_for_reply_notification.rb

@@ -10,17 +10,17 @@ class FetchUsersForReplyNotification < ActiveInteraction::Base
 
     def execute
       [].tap do |recipients|
-        recipients.push(parent.creator) if notify_parent_creator?
-        recipients.push(subject.creator) if notify_subject_creator?
+        recipients.push(parent.creator) if notify_parent_creator? && parent.creator.present?
+        recipients.push(subject.creator) if notify_subject_creator? && subject.creator.present?
       end
     end
 
     def notify_parent_creator?
-      parent.present? && !reply_to_self? && creator_wants_notification?(parent.creator)
+      parent.present? && !reply_to_self? && parent.creator.present? && creator_wants_notification?(parent.creator)
     end
 
     def notify_subject_creator?
-      on_annotation? && creator_wants_notification?(subject.creator)
+      on_annotation? && subject.creator && creator_wants_notification?(subject.creator)
     end
 
     private

api/app/views/notification_mailer/reply_notification.html.erb

@@ -1,5 +1,5 @@
 <div>
-  <%= @comment.creator.full_name %> replied to your comment on <a href="<%= @comment.subject_url %>"><%= @comment.title %></a>.
+  <%= @comment.creator&.full_name || "A deleted user" %> replied to your comment on <a href="<%= @comment.subject_url %>"><%= @comment.title %></a>.
 
   <p style="margin-top: 15px; margin-bottom: 0;">
     <em><%= @comment.body %></em>

api/app/views/notification_mailer/reply_notification.text.erb

@@ -1,4 +1,4 @@
-<%= @comment.creator.full_name %> replied to your comment on "<%= @comment.title %>."
+<%= @comment.creator&.full_name || "A deleted user" %> replied to your comment on "<%= @comment.title %>."
 
 -----------------------------------------------------------
 <%= @comment.body %>

api/spec/models/annotation_spec.rb

@@ -78,9 +78,9 @@
     expect(@annotation).to be_valid
   end
 
-  it "invalid without a creator" do
+  it "valid without a creator" do
     @annotation.creator = nil
-    expect(@annotation).to_not be_valid
+    expect(@annotation).to be_valid
   end
 
   it "enqueues a TEXT_ANNOTATED event on creation" do

api/spec/models/flag_spec.rb

@@ -15,11 +15,6 @@
   describe "is invalid when" do
     let(:flag) { FactoryBot.build(:flag) }
 
-    it "creator is nil" do
-      flag.creator = nil
-      expect(flag).to_not be_valid
-    end
-
     it "flaggable is nil" do
       flag.flaggable = nil
       expect(flag).to_not be_valid