Fork-only import users (and deactivated users)

[taoeffect]

Problem

Some users, like import users, don't accept change requests, and to edit their articles you must fork it.

Similarly, if a user deleted their account, and an article has nobody who can review change requests to it, then likewise it makes sense to only offer the option to fork the article.

Solution

• Add an attribute to user accounts that indicates they are fork-only
• Articles belonging to these users (for which there are no other users who can review change requests), inform users who are editing the article that "This will create a new article because the user doesn't accept change requests"