* DEV: Use `render_json_error` (Adds specs for Admin::GroupsController)
* DEV: Use a specific error on blank category slug (Fixes a `render_json_error` warning)
* DEV: Use a specific error on reviewable claim conflict (Fixes a `render_json_error` warning)
* DEV: Use specific errors in Admin::UsersController (Fixes `render_json_error` warnings)
* FIX: PublishedPages error responses
* FIX: TopicsController error responses (There was an issue of two separate `Topic` instances for the same record. This makes sure there's only one up-to-date instance.)
If the feature is enabled, staff members can construct a URL and publish a
topic for others to browse without the regular Discourse chrome.
This is useful if you want to use Discourse like a CMS and publish
topics as articles, which can then be embedded into other systems.
