fix workspace module / rewrite to new API

[skurfuerst]

Sebastian Helzle is currently planning a new GraphQL/React based Workspace module. Instead of fixing the old Fluid one, we can wait a bit and then implement this API.

[bwaidelich]

ideas from the ESCR weekly:

• Decide what to do with the workspace module (currently broken)
  • Can we "outsource" this topic partly to the community (i.e. start with wireframes for a module v2)
  • Dream: $someone builts a new "diff" module that we can fill via a clean API (DTO, ...)
• Nested Workspaces
• Introduce concept of "Changeset" (e.g. allow editors to switch between, annotate and explicitly mark for review -> "Workflow API")
  • Allow working in content streams that are not assigned to workspaces
• can we release a first MVP without workspace module? (How to publish nested workspaces?)
  • PRIO 1 Sebastian: Idea: patch current workspace module and remove option to publish/discard individual nodes

[skurfuerst]

@bwaidelich I would close this, as basically the workspace module works now :)