DEV: Allow with_service in jobs

This patch introduces a new `ServiceJob` class allowing the use of
`with_service` in jobs.

This way, it’s easier to use the chat service objects in jobs and
provides the same level of functionality than the one we have in
controllers.

plugins/chat/app/controllers/api_controller.rb

@@ -12,4 +12,18 @@ class Chat::Api < Chat::ChatBaseController
     raise Discourse::NotFound unless SiteSetting.chat_enabled
     guardian.ensure_can_chat!
   end
+
+  def default_actions_for_service
+    proc do
+      on_success { render(json: success_json) }
+      on_failure { render(json: failed_json, status: 422) }
+      on_failed_policy(:invalid_access) { raise Discourse::InvalidAccess }
+      on_failed_contract do
+        render(
+          json: failed_json.merge(errors: result[:"result.contract.default"].errors.full_messages),
+          status: 400,
+        )
+      end
+    end
+  end
 end