Return the created profileid/sessionid when registering an account

Libraries/SPTarkov.Server.Core/Callbacks/LauncherCallbacks.cs

@@ -24,13 +24,13 @@ public class LauncherCallbacks(
     public ValueTask<string> Login(string url, LoginRequestData info, MongoId sessionID)
     {
         var output = launcherController.Login(info);
-        return new ValueTask<string>(output.IsEmpty() ? "FAILED" : output);
+        return new ValueTask<string>(output.IsEmpty() ? "FAILED" : output.ToString());
     }
 
     public async ValueTask<string> Register(string url, RegisterData info, MongoId sessionID)
     {
         var output = await launcherController.Register(info);
-        return string.IsNullOrEmpty(output) ? "FAILED" : "OK";
+        return output.IsEmpty() ? string.Empty : output.ToString();
     }
 
     public ValueTask<string> Get(string url, LoginRequestData info, MongoId sessionID)

Libraries/SPTarkov.Server.Core/Controllers/LauncherController.cs

@@ -106,13 +106,13 @@ public class LauncherController(
     /// </summary>
     /// <param name="info"></param>
     /// <returns></returns>
-    public async Task<string> Register(RegisterData info)
+    public async Task<MongoId> Register(RegisterData info)
     {
         foreach (var (_, profile) in saveServer.GetProfiles())
         {
             if (info.Username == profile.ProfileInfo?.Username)
             {
-                return "";
+                return MongoId.Empty();
             }
         }