* Added Authentication

OrdersManagement/Services/UserService.cs

@@ -8,6 +8,12 @@ public class UserService(HttpClient httpClient)
     {
         return await httpClient.GetFromJsonAsync<IEnumerable<UserDto>>("api/Users");
     }
+    
+    public async Task<UserDto?> AuthenticateUserAsync(string login, string password)
+    {
+        var response = await httpClient.PostAsJsonAsync("api/users/authenticate", new { Login = login, Password = password });
+        return response.IsSuccessStatusCode ? await response.Content.ReadFromJsonAsync<UserDto>() : null;
+    }
 
     public async Task<UserDto?> GetUserAsync(Guid userId)
     {
@@ -19,9 +25,9 @@ public class UserService(HttpClient httpClient)
         return await httpClient.GetFromJsonAsync<UserDto>($"api/Users/by-username/?username={username}");
     }
 
-    public async Task AddUserAsync(UserDto user)
+    public async Task<HttpResponseMessage> AddUserAsync(UserDto user)
     {
-        await httpClient.PostAsJsonAsync("api/Users", user);
+        return await httpClient.PostAsJsonAsync("api/Users", user);
     }
 
     public async Task UpdateUserAsync(UserDto user)