Unfortunately I was wrong when I stated that the restriction for an association to a specific subfolder “can be cross checked server-side and configured directly within the content model using a custom constraint.” (compare my blog entry on custom categories)
Why? Cause custom constraints are only possible for properties – not for associations. Too bad as I had the constraint nearly implemented. *sigh* I would really appreciate it if Alfresco could implement this functionality also for associations. And by the way – could also a built-in constraint for subfolder-selections be integrated? This would make my work-around unnecessary.
However, while the custom constraint thing didn’t work, I managed to implement a comparable functionality to the built-in category browsing for my custom categories: I implemented a Behavior that creates respectively removes links in the linked to custom category folder. This allows to browse for documents by browsing the custom-category folders. And this is easily possible from within share through the new Repository Link. :) Stay tuned – a tutorial will soon be published on this blog.
PS: Is there someone else having a similar use-case than I have? How do or would you solve it?