Fix emby/user/public API leaking private data

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.

Emby.Server.Implementations/Library/UserManager.cs

@@ -613,6 +613,31 @@ namespace Emby.Server.Implementations.Library
             return dto;
         }
 
+        public PublicUserDto GetPublicUserDto(User user, string remoteEndPoint = null)
+        {
+            if (user == null)
+            {
+                throw new ArgumentNullException(nameof(user));
+            }
+
+            bool hasConfiguredPassword = GetAuthenticationProvider(user).HasPassword(user);
+            bool hasConfiguredEasyPassword = !string.IsNullOrEmpty(GetAuthenticationProvider(user).GetEasyPasswordHash(user));
+
+            bool hasPassword = user.Configuration.EnableLocalPassword &&
+                !string.IsNullOrEmpty(remoteEndPoint) &&
+                _networkManager.IsInLocalNetwork(remoteEndPoint) ? hasConfiguredEasyPassword : hasConfiguredPassword;
+
+
+            PublicUserDto dto = new PublicUserDto
+            {
+                Name = user.Name,
+                HasPassword = hasPassword,
+                HasConfiguredPassword = hasConfiguredPassword,
+            };
+
+            return dto;
+        }
+
         public UserDto GetOfflineUserDto(User user)
         {
             var dto = GetUserDto(user);