You can use hooks for user collection. You are getting "IndirectCollectionAccessDisallowed" because the URL for calling user collection was wrong.
As we know that there is an issue with 'Testing' button in the hook editor for Users collection and you can not use it for testing.
But you can use Kinvey API console for testing on Users collection. Once you login into the console and select your app, you can click on "API Console".
You can call different functions on Users collection and the Users collection hooks will get executed. You can confirm it in hook editor logs.
Please take a look at Basic User Operations.
Thanks for this explanation. But how to make "Testing" environment in hook editor to make call to /user and not to /appdata ? I do not see any possibility in the editor interface to change it. It shouldn't be like that editor will choose appropriate end point while testing?
It was not my fault to select wrong path, but Testing environment in hook editor. How to change this? It makes Testing useless for user collection...