Enable read-only custom_attributes
Description
Based on current implementation, only admins can GET the custom attributes.
However, this is unusable in case where admins sets the value which is supposed to be read by other users. (Include problem, use cases, benefits, and/or goals)
Proposal
Would be great is GET of custom attributes can be made possible to the specific users on their resources.
We can have something like PUT /users/readable_custom_attributes and provide array of keys that are opened to the users.