exception if agentName is empty

src/Managing.Application/Users/UserService.cs

@@ -146,6 +146,9 @@ public class UserService : IUserService
 
     public async Task<User> UpdateAgentName(User user, string agentName)
     {
+        if (string.IsNullOrEmpty(agentName))
+            throw new Exception("Agent name cannot be empty");
+
         // Check if agent name is already used
         var existingUser = await _userRepository.GetUserByAgentNameAsync(agentName);
         if (existingUser != null)