Ability to add only one occurrence of a block/widget to a homebox in D8

@Grevil: Any ideas where we could put this in the new concept?
Perhaps per HomeboxType we should add a list for HomeboxPortletTypes to select different options for them within this specific homebox type:

Status (Select):

• Allowed: Once instance
• Allowed: Unlimited instances
• Disallowed

Any better ideas for naming?

And only allowed portlet types can be used in the Homeboxes of this type?
New portlets should NOT be available by default, so you have to enable them explicitly.

I think that's a good concept!

This is now fixed in 3.0.x! 🎉🎉🎉

Automatically closed - issue fixed for 2 weeks with no activity.