Merge branch 'master' into feature/gb/manual-actions-protected-branches-permissions

* master: (274 commits)
  Update VERSION to 9.2.0-pre
  Update CHANGELOG.md for 9.1.0
  Update Auto Deploy documentation
  Disable import URL field in New project form since it's hidden by default
  Remove reference to burndown charts since they don't exist for ce.
  Use master_password for Sentinel
  Refactor Discussions docs
  Start versioning cached markdown fields
  Refactor add_users method for project and group
  Improved the spec Now correctly tests against different forms
  Refactor environments components into vue files - part 3
  Adding animation for all dropdown
  fix placeholder visibility
  submodule_links: handle urls that don't end with .git
  Add help regarding vue resource and where to include it
  Append .json to ajax endpoint to prevent browser to display raw json
  Fixed the preview keyboard shortcut focusing wrong tab
  Fix broken link
  Added new discussions docs
  Started on resolvable discussions docs
  ...