It is the follow-up to our discussion with recena and jglick.

The current Item categorization uses JENKINS_URL/categories endpoint to provide the list of categories.

It causes several concerns:

• Categories apply to items only, but the "/categories" endpoint does not mention it in paths. Once we want to implement slave categories, it may become a problem
• The endpoint may conflict with existing closed-source plugins. E.g. I had the Categorization plugin at one of my previous companies, which used the similar endpoint. Update to 2.0 will cause regressions in such plugins
• The implementation is not pluggable. E.g. Views and Items cannot filter the categories somehow

Proposed solution:

• Ship categories via VIEW_URL/itemCategories
• Allow overriding of the method in views. Just for the future pluggability