IIRR-30(auto): Skip user token check for Slack controllers

Added skip_before_action :check_user_token to Slack::ApplicationController
to bypass user token verification for Slack requests. This ensures that
Slack webhooks and interactions are not blocked by user authentication
requirements.

Ref: https://ombulabs.atlassian.net/browse/IIRR-30

Author: fbuys

app/controllers/slack/application_controller.rb

@@ -1,5 +1,7 @@
 class Slack::ApplicationController < ApplicationController
   skip_before_action :verify_authenticity_token
+  skip_before_action :check_user_token
+
   before_action :valid_slack_request?
 
   private