Show issue/epic navigation consistently in groups and projects

Proposal

In order to support group-level issues, and project-level epics (design issue, feature epic), we need to make navigation elements accessible that are currently in only a group or project so that users can find and manage those items. Specifically this proposes:

• Global "Create new" menu:
  • show "New issue" in groups with group-issues enabled (currently only in projects)
  • show "New epic" in projects with epics enabled (currently only in groups)
• Plan section:
  • Show "Epics" and "Epic boards" in projects where Epics are enabled, pointing to new project-level epics pages
    • We are still considering the possibility of consolidating issues/epic views, but any changes there would be separate from this effort and follow later.

In all cases these navigation elements already exist — no totally new elements are proposed, or any changes to naming, only the logic of when they're shown.

Other locations that were considered

Given the established patterns, and a desire to ensure parity and consistency across groups/projects, no other locations were identified that could meet those goals.

We have explored more comprehensive reorganizations of how issues/epics are managed, which have different approaches to navigation, but that is beyond the scope of group/project parity for issues/epics.

Checklist

• Review the handbook page for navigation changes
• Add relevant information to the issue description detailing your proposal, including usage and business drivers.
• List at least two other places you considered to introduce your feature
• Add relevant designs to the Design Management area of the issue
• Ensure your UI suggestion align with the Documentation Style Guide
• Engage Technical Writing. They can help craft a term that best describes the feature(s) you’re proposing.
• Follow the product development workflow validation process to ensure you are solving a well understood problem and that the proposed change is understandable and non-disruptive to users. Navigation-specific research is mandatory for additions or when restructuring.
• Engage the Foundations Product Manager for approval. The Foundations DRI ( @cdybenko) will work with UX partners in product design, research, and technical writing, as applicable.
• Consider whether you need to communicate the change somehow, or if you will have an interim period in the UI where your item will live in more than one place.
• Ensure engineers are familiar with the implementation steps for navigation.