Real-time issue relationships widget

Follow up to https://gitlab.com/gitlab-org/gitlab-ee/issues/2001.

• View these in the widget:

  • Related merge requests which close the current issue

  • Related merge requests which do not close the current issue

  • Related branches

• Update this entire widget in real-time using the correct CSS transitions.

added Stretch in GitLab FOSS label

changed milestone to %9.2 in gitlab-foss

added feature proposal in GitLab FOSS label

mentioned in issue gitlab-foss#21453 (closed)

added real-time in GitLab FOSS label

changed milestone to %Backlog in gitlab-foss

added 897282 gitlab-foss217506 and removed Stretch in GitLab FOSS labels

mentioned in issue gitlab-foss#33102 (moved)

changed milestone to %Next 2-3 months in gitlab-foss

removed to schedule in GitLab FOSS label

mentioned in merge request gitlab-com/www-gitlab-com!6345 (merged)

moved from gitlab-foss#31123 (moved)