RAC - RDP Session without preserved user credentials not allowed

**Is your feature request related to a problem? Please describe.**

I have configured an RDP connection in the new RAC Outpost. Here I have to set a valid username and password for the remote Windows system, otherwise I get an "Authentication failure" error when opening the session.

To do this, I have to store the Windows credentials in the Admin section of Authentik and create a "RAC Provider Property Mapping" for each user. Also, each user has to enter his password in the admin section.

With this limitation, the Parallel Sessions feature is very limited.

**Describe the solution you'd like**

I want to open an RDP session to a Windows system and use the Windows system's logon screen.

This allows multiple users to have parallel sessions on the remote system using their logon credentials.

**Describe alternatives you've considered**

Not user friendly to configure a property mapping for each user.

**Additional context**

In Apache Guacamole (same remote backend), the username and password are optional in an RDP session configuration.