remove userId from ClientCredentialsMessage.cs

(cherry picked from commit 5b4e0e3)

Author: st0ffregen

service/backend/Models/ClientCredentialsMessage.cs

@@ -4,8 +4,5 @@ public class ClientCredentialsMessage
 {
     public byte[] ClientCredentials { get; set; } = [];
     public required string MemoryKey { get; init; } = string.Empty;
-    
-    public int UserId { get; init; }
-    
     public required string AgentName { get; init; } = string.Empty;
 }