Hide Runn support users from the users endpoints

Runn support (superuser) accounts are no longer returned by GET /users or GET /users/USERID. PATCH /users/USERID, DELETE /users/USERID, GET /users/USERID/views, POST /users/USERID/views/{viewId} and DELETE /users/USERID/views/{viewId} now return 404 Not Found for them. As a result, superuser is no longer a possible value of permissions.type or permissions.userType in user responses.