Nested Milestones - Sub-Milestones

Problem to solve

if a major milestone like a release consists of multiple smaller milestones, it would be nice to be able to "group" them together in form of another milestone, in order to see the overall progress in the outer milestone.

Intended users

Developers and project managers can/might be interested in this feature.

Further details

consider following:

• August Release
  • Resolve Jan.Rel. Bugs (Milestone 1)
    • An issue in subsystem X
    • An issue in subsystem y
    • ...
  • Implement Nested Milestones (Milestone 2)
    • Update Milestone Feature
    • Update Issues Feature
    • Update Dashboard
  • Next Milestone
    • Issues ...
  • Issue assigned directly to this release

Proposal

Milestones should be assignable to other milestones (I would propose a 1 to 1 relation). the completion percentage of the container can be calculated based number of completed sub milestones/issues.