Allow a more advanced API feature for managing users in the site.

At the moment, the user creation api is provided by POST /rest/api/3/user endpoint. This endpoint currently generates inconsistent results and there are no additional create options available.

It would be useful to have additional advance options when managing users via API.

• Set if the new user has site access or not (inactive)
• Choose a product access to grant for new user
• Query the product access for each user.
• Change the product access, site access status of an existing user.