This commit fixes the emby/user/public API that was returning more data
than necessary. Now only the following information are returned:
- the account name
- the primary image tag
- the field hasPassword
- the field hasConfiguredPassword, useful for the first wizard only
(see
https://github.com/jellyfin/jellyfin/issues/880#issuecomment-465370051)
- the primary image aspect ratio
A new DTO class, PrivateUserDTO has been created, and the route has been
modified in order to return that data object.
