Trim attributes that are not useful from `WebHookTopicViewSerializer`.

app/serializers/web_hook_topic_view_serializer.rb

@@ -1,11 +1,18 @@
 require_dependency 'pinned_check'
 
 class WebHookTopicViewSerializer < TopicViewSerializer
-  def include_post_stream?
-    false
-  end
 
-  def include_timeline_lookup?
-    false
+  %i{
+    post_stream
+    timeline_lookup
+    pm_with_non_human_user
+    draft
+    draft_key
+    draft_sequence
+    message_bus_last_id
+  }.each do |attr|
+    define_method("include_#{attr}?") do
+      false
+    end
   end
 end

spec/serializers/web_hook_topic_view_serializer_spec.rb

@@ -0,0 +1,30 @@
+require 'rails_helper'
+
+RSpec.describe WebHookTopicViewSerializer do
+  let(:admin) { Fabricate(:admin) }
+  let(:topic) { Fabricate(:topic) }
+
+  let(:serializer) do
+    WebHookTopicViewSerializer.new(TopicView.new(topic),
+      scope: Guardian.new(admin),
+      root: false
+    )
+  end
+
+  it 'should only include the required keys' do
+    count = serializer.as_json.keys.count
+    difference = count - 35
+
+    expect(difference).to eq(0), lambda {
+      message = ""
+
+      if difference < 0
+        message << "#{difference * -1} key(s) have been removed from this serializer."
+      else
+        message << "#{difference} key(s) have been added to this serializer."
+      end
+
+      message << "\nPlease verify if those key(s) are required as part of the web hook's payload."
+    }
+  end
+end