Feature/Epic Board for Workspace Lines Merged

We would love to use Workspace Lines to group work from different product areas together, but almost all of our work happens on the Epic Board, since it's the best view of the work in Progress.

We don't want to have multiple Epic Boards because it will mean splitting up the view we have of our work and make it harder for casual users to find what they're looking for.

IF workspace lines would show a combined view of the epic boards within the workspaces contained in the line, we could happily use a workspace per product area, while keeping the central view of our work alive.