Currently, the /api/v1/users/USER_ID endpoint for getting a single user by _id (https://developers.hive.com/v1.0/reference/get-user) only works if the user ID passed is that of a normal workspace member.

We need to update this endpoint to do a check which includes external users, as well as normal members, when checking for whether a user can be accessed from the list of workspaces the user requesting via the API is in.