Context

• ~"EE Premium"

Description

• Extension of #2001 (closed) and similar UI to manage blocking issues.
• An issue cannot be closed until it's blockers have all been closed. Only applies when an issue is open.
• A given issue can have any number of blocking issues.
• Consider an issue that we are attempting to close right now. If there is at least one blocking issue, then that issue fails the closing attempt.
• This applies to different scenarios where an issue is attempted to be closed.
  • Closing manually in the GitLab UI.
  • Closing via the API
  • Closing via auto-closing: https://docs.gitlab.com/ee/user/project/issues/automatic_issue_closing.html with commits and merges.