Check for GitLab token

config.sample.yml

 ---
 issue_tag: RT
+token:
 rt:
   server: https://rt.example.org/
   user: gl-bridge

gl-rt-bridge.rb

@@ -16,6 +16,9 @@ rt = RT_Client.new(server: settings.rt[:server],
                    cookies: settings.rt[:cookies])
 
 post '/' do # rubocop:disable Metrics/BlockLength
+  if not settings.token.nil?
+    halt 403 unless request.env['HTTP_X_GITLAB_TOKEN'] == settings.token
+  end
   gitlab_event = request.env['HTTP_X_GITLAB_EVENT']
   case gitlab_event
   when 'Push Hook'