• Edit file Gemfile.lock lalu tambahkan 
  nano /opt/openproject/Gemfile.lock
  PATH
    remote: modules/gitlab_integration
    specs:
      openproject-gitlab_integration (2.1.4)
        openproject-webhooks
  Pada block DEPENDENCIES tambahkan
    openproject-github_integration!
    openproject-gitlab_integration!
    openproject-job_status!
• Edit File Gemfile.modules 
  clone gitlab modules, lalu pindahkan ke dalam /opt/openproject/modules (tergantung path instalasi)
  git clone https://github.com/btey/openproject-gitlab-integration.git --depth=1 modules/gitlab_integration
  nano /opt/openproject/Gemfile.modules
    gem 'openproject-gitlab_integration',        path: 'modules/gitlab_integration'
  
  
• Kalau ada error ArgumentError in OpenProject 13.0.7(ArgumentError: missing keyword: :permissible_on), edit File nano /opt/openproject/modules/gitlab_integration/lib/open_project/gitlab_integration/engine.rb
  
        project_module(:gitlab, dependencies: :work_package_tracking) do
          permission(:show_gitlab_content, {})
        end
  
  
  
• Lakukan konfigurasi ulang openproject
  openproject configure
  openproject config:set OPENPROJECT_HTTPS=true
  Lalu restart openproject
  systemctl restart openproject

Check module apakah sudah terinstall pada aplikasi openproject (Administration/Plugins)