Ensure representer#to_hash is called as system user

The getter was only called outside the user system block,
which caused the custom fields to not be visible

modules/webhooks/app/workers/attachment_webhook_job.rb

@@ -38,10 +38,7 @@ def accepted_in_project?
     webhook.enabled_for_project?(project.id)
   end
 
-  def payload_representer
-    User.system.run_given do |user|
-      ::API::V3::Attachments::AttachmentRepresenter
-        .create(resource, current_user: user, embed_links: true)
-    end
+  def payload_representer_class
+    ::API::V3::Attachments::AttachmentRepresenter
   end
 end

modules/webhooks/app/workers/project_webhook_job.rb

@@ -39,10 +39,7 @@ def accepted_in_project?
     end
   end
 
-  def payload_representer
-    User.system.run_given do |user|
-      ::API::V3::Projects::ProjectRepresenter
-        .create(resource, current_user: user, embed_links: true)
-    end
+  def payload_representer_class
+    ::API::V3::Projects::ProjectRepresenter
   end
 end

modules/webhooks/app/workers/represented_webhook_job.rb

@@ -68,14 +68,22 @@ def payload_key
     raise NotImplementedError
   end
 
-  def payload_representer
+  def represented_payload
+    User.system.run_given do |user|
+      payload_representer_class
+        .create(resource, current_user: user, embed_links: true)
+        .to_hash # to_hash needs to be called within the system user block
+    end
+  end
+
+  def payload_representer_class
     raise NotImplementedError
   end
 
   def request_body
     {
       :action => event_name,
-      payload_key => payload_representer
+      payload_key => represented_payload
     }.to_json
   end
 end

modules/webhooks/app/workers/time_entry_webhook_job.rb

@@ -31,10 +31,7 @@ def payload_key
     :time_entry
   end
 
-  def payload_representer
-    User.system.run_given do |user|
-      ::API::V3::TimeEntries::TimeEntryRepresenter
-        .create(resource, current_user: user, embed_links: true)
-    end
+  def payload_representer_class
+    ::API::V3::TimeEntries::TimeEntryRepresenter
   end
 end

modules/webhooks/app/workers/work_package_webhook_job.rb

@@ -31,10 +31,7 @@ def payload_key
     :work_package
   end
 
-  def payload_representer
-    User.system.run_given do |user|
-      ::API::V3::WorkPackages::WorkPackageRepresenter
-        .create(resource, current_user: user, embed_links: true)
-    end
+  def payload_representer_class
+    ::API::V3::WorkPackages::WorkPackageRepresenter
   end
 end